Sunday, November 6, 2011

Rifle Shooting Positions: The Offhand Stance

Well, it has been a while since the last post on this blog, so let's continue where we left off: shooting positions. In this post, we will look into various rifle shooting positions.

The most common shooting positions used in rifles are: off-hand, kneeling and prone position. The sitting position is used to a lesser degree and the back position is not used as much these days. We will discuss all of them in this and subsequent posts.

It must be noted in our discussions, that we take the perspective of a right-handed shooter. For left handers, one may substitute "left" for "right" and vice-versa.

The first position we will study is the off-hand position, otherwise known as the standing position:

Image taken from W.W. Greener's The Gun and its Development, 1910. Image is now in public domain. 
Click on image to enlarge

This is a commonly used position, often used for shorter ranges and in the field. It is also taught by the US military. Notice that the feet are positioned about a shoulder width apart. The left foot is forward and pointing roughly in the direction of the target and the right foot is placed back and is almost at a right angle to the target. The legs are positioned to give the shooter a firm stance. The rifle is positioned across the chest of the shooter and the left hand is located comfortably gripping the fore-grip. Notice that the left elbow is right below the rifle, not angled to one side.

It might be worthwhile to note that in the above image, we notice that the left arm is somewhat extended out. This is called the "arm-out" off-hand position and is more suitable for shooting at moving targets, because it allows the user to rotate the upper body easier to track a target.

For a more static target, some users prefer to position the left arm much closer to the body (i.e. the arm-back offhand stance)

Notice that in the above image, the left hand is positioned close to the rifle action and the left elbow is very close to the body. While the arm-back position allows for more steadiness, it doesn't allow the user to readjust as easily as the arm-out position, if the target moves. Hence, this stance is more commonly used against static targets.

In the next post, we will look at the kneeling position.

Sunday, September 11, 2011

September 11th 2011 - Never Forget!

September 11th - Never Forget.

Sunday, August 14, 2011

Shooting Positions

In the next series of posts, we will look into the subject of shooting positions. There are many positions that one may shoot a firearm from: standing upright, kneeling, lying down, holding the firearm with only one hand, holding it with both hands, standing sideways and (if John Woo movies are any authority on shooting) jumping out of a door with a Beretta 92F pistol in each hand and firing alternately while in the air in slow motion, while a flock of white doves fly out :).

Back in the days when muzzle loaders were popular and rifling was non-existent, soldiers generally stood upright in lines of three and shot at each other. There were good reasons to do this:

  1. Without rifling, firearm accuracy wasn't very good. But if you lined up a group of men and asked them to shoot at a group of targets, chances were good at least one of them would hit a target, even if it wasn't the target he was aiming for.
  2. With a muzzle loader, the user stands it upright with the butt on the ground, pours some gunpowder into the barrel via the muzzle, then inserts a ball and wadding into the muzzle and then rams them down the barrel with a ramrod. These operations are not possible to do sitting down, especially when the muzzle-loader is some 4-5 feet long.
  3. It was considered more macho and gentlemanly by Europeans, to shoot from a position where the enemy can see you,  rather than shooting the enemy from behind cover.

In the early 1800s to about the 1840s, the British rifleman had a rifle with a handle extending down from the trigger guard. When this was grabbed with the left hand, it put the left arm at an angle that steadied it against the body.
A British Rifleman from the 1800s. Image taken from W.W. Greener's The Gun and its Development, now in public domain. Click on the image to enlarge.

This was a common position used by many European armies and shooting enthusiasts in the early 1800s.

We also have this account by a Dr. Scoffern, that describes the technique of shooting used by Swiss shooters:
"As regards the Swiss system of loading and firing, both are peculiar. The Switzer unslings a powder-flask of large dimension and turns in a charge of about 2.5 drams of powder. From a side pocket, he next extracts a linen patch, and, putting it into his mouth, turns it round and round, very much as Jack turns his quid. The Switzer's object is to saturate his patch with saliva. This is his way of solving the lubrication difficulty, and, mind me, it is not a bad one. His next move is to lay the patch upon the bore and the picket upon that: which being done, he takes the ramrod in both hands and drives the picket home with one thrust. To be assured that it is home, the Switzer jerks the ramrod down upon it with a ringing thwack. 'Bad practice,' you say: 'he meals the powder'. Not a bit of it! At the end of the ramrod there is a flat iron boss, which only permits it to fall down to a fixed and unvarying extent. Well, the anxious moments of firing are now come round. See how the Switzer employs them. He begins by planting his legs wide apart, left leg foremost. He tries the ground under him for a moment or so, to find whether it be soft, and if he can wriggle out two little graves, one for each foot, the better. Should you have turned away your eye for a moment, and then direct your glance at the Switzer again, you would have found him half as big again as you last saw him. He has puffed himself out with a deep breathing, like the frog who aspired to become a bull. By this deep inspiration, the Switzer has stiffened himself, just after the way one takes the limpness out of a macintosh cushion -- by filling it full of wind. The Switzer is firm planted and rigid now -- he could no more bend from side to side than can a hard rammed sausage. If he were obliged to hold his wind as long as we take to tell our tale, it would be bad for him -- he would burst outright, like an overcharged rifle. Well, with legs apart (like a little Rhodian Colossus) and bated breath, the Switzer shoulders his piece. At the end of the stock is a boss, which he tucks between his right arm and right ribs. Gathering his two hands close together, he rests his rifle on his left hand, placed close in front of the trigger guard; pressing his left elbow, not on the left knee, indeed, but upon the left hip. Lot's wife could hardly be more rigid. Limited power of motion, nevertheless, the Switzer has. Heavenward you see his rifle pointing, and if you observe the Switzer's nose (that organ given only for ornament, as some affirm), it has turned to a purpose of utility. The Switzer is steadying the butt-end of his rifle against it; his nose is a lateral rest. By this time that nose is red on the tip, the face turgid, the eyes projecting. The Switzer's whole position is decidedly not graceful -- one very suggestive of extrusion. Heavenward you see it pointing. Gradually down and down it drops. The blank is seen, the trigger pressed. Rifle crack and Switzer's grunt follow on the heels of each other. He could not hold his breath for ever. Picket and unpreserved breath fly together. Behold him now, panting and puffing like a Cingalese pearl-diver fresh from the worrying of a ground shark. Decidedly, our style of rifle-firing is more graceful and quick."

Method of holding Rifle and Position of Swiss Rifle Shot. Click on image to enlarge. Public domain image.

While Dr. Scoffern might not have thought the Swiss style as "graceful", it was a very effective style, as the Swiss won the majority of prizes as the first British National Rifle Association competition held at Wimbledon in 1860. It must be noted that the Swiss shooters made sure that they had a stable shooting position before pulling the trigger, something that is still emphasized in training today.

In the next few posts, we will look into more shooting positions, both historical and modern.

Monday, August 8, 2011

Cleaning Firearms: Modern Methods

In the last post, we studied some historic instructions on cleaning firearms. Actually, most of what was stated in that post still hold true today, though some of the cleaning solvents and materials have changed. So here's how a firearm owner cleans his weapon these days:

  1. Weapon is unloaded by the person cleaning the weapon. Person points the firearm in a safe direction, makes sure finger is far away from the trigger, magazine is removed and he/she also checks the chamber to make sure that there isn't already a cartridge in the chamber and also enables any safeties. Remember: SAFETY FIRST!
  2. Person disassembles the firearm for cleaning, only so far as recommended by the manufacturer's manual. Typically, disassembly should only involve removing a few parts at most (field stripping). It is not necessary, for example, to disassemble the entire trigger assembly to clean a firearm. If more extensive work is required, it is probably best to consult a competent gunsmith.
  3. After the person field strips the firearm, he or she visually inspects the parts for signs of excessive wear or damage. If any problems are seen, it is best to send it to a gunsmith immediately.
  4. The person cleaning the firearm should have a cleaning kit available. Most commonly available kits have a cleaning rod (usually one that is disassembled into multiple parts), a few cotton cloth cleaning patches, a couple of patch holders or jags (or both jags and cloth holders) that attach to the end of the cleaning rod and to which a cloth patch is attached, a bore brush whose diameter depends on the firearm being cleaned, a hand brush, assorted solvents and gun greases and a bottle of gun oil. The user may augment this kit with extra brushes, jags, cloth holders and patches of different diameters, especially if the user owns multiple firearms of different bores. Sometimes, additional cleaning rods may also need to be purchased in appropriate diameters for different calibers.
  5. When possible, the user always tries to clean from the breech end towards the muzzle (i.e.) following the same direction as the bullet. If it is not possible to do it in this direction (for instance, in some revolvers), then one should take precautions to not push any debris into the action of the firearm. Some cleaning kits include a muzzle guard for situations where cleaning is done from the muzzle end.
  6. The barrel contains a couple of types of fouling: the first is due to powder residue (powder fouling) and the second is metal fouling, which is caused by metal particles from the cartridge case (brass) and metal particles from the bullet itself (lead and copper) getting deposited into the rifling grooves. There are different solvents that deal with powder fouling vs. metal fouling and some solvents (such as Hoppe's #9) do both.
  7. The user first attaches a patch holder or a jag to the cleaning rod and attaches a cotton patch cloth at the end. The user then soaks the patch with suitable solvent and pushes it completely through the bore. This removes some of the loose powder and metal fouling in the barrel.
  8. The user removes the patch holder and attaches the appropriately sized bore brush to the cleaning rod. Then the user soaks the brush in more solvent and pushes it through the bore again. As the user does this, the brush turns as it engages the rifling in the barrel. The user completely pushes the brush through the barrel, until the brush emerges on the other side and then pulls it back completely through and repeats the process 12-20 times. This loosens all the tiny metal particles and fouling that are stuck in the rifling grooves. It is not a good idea to reverse direction with the brush while it is still inside the barrel, because it will ruin the brush prematurely.
  9. The user then leaves the barrel aside to soak the solvent for around 5 minutes, so that the solvent has a chance to dissolve some of the lead or carbon buildup still clinging to the barrel. In the meantime, the user grabs the hand brush (or even an ordinary toothbrush), dips it in more solvent and uses it to brush the exposed action, receiver, bolt, trigger assembly etc. and remove the gunpowder residue in here.  The user then dries all the scrubbed parts with a clean dry cloth.
  10. After the solvent has had a chance to work its magic inside the barrel, the user then takes the cleaning rod and attaches a cloth holder or a jag tip to the end and attaches a clean dry patch on it. The user then pushes it through the barrel completely. Most likely, this patch will come out very dirty. The user then replaces the patch with a new clean one and then repeats the process again for a few times, until the patch comes out looking relatively clean.
  11. The user then applies a few drops rust-preventative to a clean cloth patch and runs it down the barrel again. This leaves a very thin coating of rust preventative solution in the barrel bore, The user may also apply this to the outside of the barrel as well.
  12. The user then applies a very little amount of gun oil to lubricate the metal parts recommended in the manual. It is not a good idea to use too much gun oil for guns with wood stocks, as the excess oil could soak into the wood stock and ruin it (gun oil is very different from linseed oil and has a detrimental effect on wood). Excess oil also collects dust and dirt much easier, so it is a good idea to apply very little gun oil indeed, unless the gun is intended to be stored away for a while.
  13. For the same reason, it is not a good idea to put solvent or lubricant inside the magazine because the excess gun oil will collect dirt and dust in the magazine, while solvent will react with the cartridge casings and primer and degrade them. Magazines should only be cleaned with dry brushes if needed.
  14. Finally, the user uses a small flash light to look up through the barrel to make sure it looks clean.
  15. The user then reassembles the firearm and uses a silicone cloth to wipe away any finger prints.
Instead of a cleaning rod, some people use a bore snake instead. This is a long flexible cord with a section of brushes and cotton cloth on one end. The user merely drops the cord through the barrel and pulls it through to the other end. A couple of runs of this and the barrel is clean and ready to go.

Lastly, before we leave, here's a few videos that demonstrate what we just discussed above:

Happy viewing!

Cleaning Firearms: A Historical Perspective

In our discussion about carrying conditions a little while ago, it was mentioned that condition 4 is generally used by people who plan to store their firearms for a long while in a gun vault or safe (say, at the end of the hunting season). Which brings up a side topic -- the user also cleans their firearms before putting them into storage. This inspired the next series of articles which are going to deal with the subject of cleaning firearms.

First, we will look at some instructions for sportsmen, reproduced from W.W. Greener's book The Gun and its Development, Ninth Edition from 1910. Bear in mind that this was written for the English sportsman of the early 1900s. So while some of the cleaning equipment and solvents may appear to be a bit antiquated, these were possibly the best available from around 1850 to the early 1900s. The instructions proceed as follows:

To clean a gun after a day's shooting. If a gun be wet, it should be wiped dry at once, but the cleaning of the barrels and breech-action may be left until the sportsman or his servant has time to do it properly.

To clean the barrels. Use the cleaning-rod, with tow and oil, or turpentine. To remove the fouling, put muzzles on a piece of wood, and push the rod down to within an inch of the muzzle, and draw up to the chamber. Do this two or three times; and push right through. Use the bristle brush, or the rod with plenty of flannel; finish with the mop soaked in refined neatsfoot, pure Arctic sperm oil, or vaseline.

Never half-clean the barrels; always wipe them dry and clean before finally oiling, and do not put the mop used for oiling into a foul barrel. To remove leading from the inside of a gun barrel, soak well with turpentine; then clean well with a bristle brush, or even with a wire brush, but never use emery if the shooting qualities of the gun are valued.

Always wipe the bed, face, and joint of the breech-action with an oily rag or flannel. A little linseed oil may be rubbed over the stock occasionally.

Before putting the gun together, ascertain that all the bearing parts are free from dust and grit.

The joint may be lubricated with a mixture of half best Russian tallow and half petroleum. In most hammerless guns, if the cover plate underneath the breech-action body is taken off, the locks may be inspected, oiled, and any rust or clogged oil and dust removed from the bent.

The cocking-lifters of hammerless guns, the holding-down and top bolts, and the triggers, if they have a tendency to clog, may be touched up with a knitting-needle dipped in petroleum. They must be lubricated, whenever they require it, with chronometer oil, Rangoon oil, or finest neatsfoot.

Do not use a feather for the purpose of putting on any lubricant; a wire knitting-needle or bodkin is much better.

To remove rust from the inside or outside of a barrel, procure a tub, and with a kettle of boiling water well scald the barrels inside and out, inserting a wooden peg in one of the barrels to hold them by, wipe perfectly dry with flannel, and then oil. It is as well to do this before putting the gun aside for any length of time.

If the barrels are foul through using inferior powder, and the fouling has become hard and dry, cold water, or hot soap-suds, may be used to cleanse them. Water boiling hot kills rust.

Turpentine, often used successfully to clean the residue from gun barrels, will give great trouble if it gets into the fine-fitting parts of the mechanism of the breech-action and locks, and must therefore be used with care.

Rusty or tight breeches in muzzle-loading barrels may often be turned out, providing the breech-ends of the barrels have been soaked in petroleum, Very obstinate breeches may require to be well heated, as well as lubricated, before they can be turned out, but usually petroleum will be found a sufficient remedy for incipient rust of the working parts. All the parts of the mechanism may be cleaned with petroleum; it removes clogged vegetable and animal oils well.

So that was quite the read, wasn't it. A brief word on some of the solvents mentioned in the book:

Tallow is made by rendering the fat of beef or mutton, especially the fat found around the loins and kidneys of the animal. The process of "rendering" is as follows: raw fat is ground up and then placed in a vessel and heated with steam to drive off the moisture. As the moisture is removed, the fat is released from the fat cells. This fat is percolated off and the remaining solids are squeezed under pressure to release more fat as well (or they may be separated using a centrifuge). The tallow fat is a yellow liquid when hot, but cools down to a white creamy solid at room temperature.
Tallow being made. Note that it is currently a yellow liquid, as the tallow is still hot.

The tallow after it has cooled down to room temperature.

The tallow fat was traditionally used for soap-making, candle-making, food (it didn't spoil easily even without refrigeration), lubrication of  locomotive and steamship engines etc. Russian tallow was traditionally made from mutton mainly and by the 1860s, it was cheaper to obtain in England than English-made tallow and was much more available than tallow from other British colonies such as Australia, New Zealand, the East Indies and South America. People still make tallow today, for use in food (McDonalds used tallow for cooking french fries until 1990), lubrication, high end shaving soap, shoe polish, bio-diesel etc.

Neatsfoot oil is also still around today. Like tallow, it is also made by rendering beef parts, however the parts used are only the shin bones and feet (minus the hooves) of cattle. In fact, the word neat is an old word for cattle, which is where the word neatsfoot comes from. The resulting oil is a light yellow color. Neatsfoot oil is still made today and mainly used for conditioning leather products. It is available at places like or Walmart.

Click on image to enlarge. Public domain image.

Arctic Sperm Oil is a bit of a misnomer, as it is not actually made from the Sperm whale, but from the Northern Bottlenose whale, Hyperoodon Rostratus. This whale is a lot smaller (adult size is about 32 feet long) than the sperm whale and is found in the northern arctic waters between Europe and North America. Whalers in the 19th century found that this whale is also capable of producing oil that is very similar in chemical composition to Sperm Oil from the Sperm whale, but its oil has a more pronounced tendency to "gum" up at lower temperatures, which is why Arctic Sperm Oil was always sold cheaper than the true Sperm Oil. Because the two oils could not be told apart easily, some unscrupulous producers of Sperm Oil would sometimes adulterate their product with the cheaper Arctic Sperm Oil. Note that while both Sperm Oil and Arctic Sperm Oil were used as lubricants, but Mr. Greener appears to be recommending the cheaper of the two. Both oils were used for oil lamps and candle production, but were gradually replaced by cheaper petroleum products starting in the 1850s. However, they were still used as lubricants well into the 1960s. As of the late 1960s and 1970s, due to whaling restrictions, neither oil is available in the market these days. Animal conservationists will be happy to note that the Northern Bottlenose whale species is thriving again and the species population status is classified as "least concern". Sperm whales are also on the path to recovery and are now classified as "vulnerable" rather than "endangered".

Chronometer oil was made from extracting the oil from the head and jaws of the porpoise family (i.e.) porpoises, pilot whales, killer whales etc., in a very similar process to extracting the oil from sperm whales and bottlenose whales. It was used to lubricate the working parts of fine watches and ships' chronometers. As with sperm oil, it is no longer used and is replaced by other alternatives.

Petroleum is also mentioned. Petroleum was known about 4000 years ago, chiefly because it was available from natural oil springs in the Middle East. By the 1850s, the process of refining petroleum to produce kerosene was invented and drilling started soon after. However, petroleum refining really took off only after automobiles became popular. Before then (as in the early 1900s), it was possible to buy raw petroleum at the local chemists.

Linseed oil is made by pressing seeds of the flax plant. The oil is edible, but it is mainly used in paints, as a hardener for putty, in the manufacture of linoleum and as a wood finish. Linseed oil was traditionally used to finish wood gun stocks for centuries and it still continues to be used for that purpose.

Rangoon oil is actually a heavy petroleum distillate roughly along the lines of kerosene and fuel oil. It has a slow evaporation rate and was used as a rust preventative by the British around the 1850s. They found that it worked rather well, especially in hot and steaming jungles. The name comes from the fact that the first source was from a natural oil well found in Rangoon (now Yangoon), Burma (now Myanmar).

Rangoon oil may still be purchased today, especially from dealers who deal with antique and fine custom-made firearms.

Tuesday, August 2, 2011

Safety Mechanisms: Carry Conditions

With all the discussion about safety mechanisms in the previous few posts, it is now time to discuss the subject of carry conditions, i.e. how to carry a firearm in various conditions of readiness. The various carry conditions were defined by the legendary Marine Lieutenant Colonel John Dean ("Jeff") Cooper, who did much to teach the modern techniques of handgun shooting.

Before discussing the various carry conditions, it must be noted that Lt. Col. Cooper was a big fan of the Colt M1911 and its variants. So when he defined his carrying conditions, it was with such a pistol in mind (i.e.) a semi-automatic with an exposed hammer. Therefore, some of the carry conditions may not apply to other firearm types. With that said, let us discuss the various carry conditions (from safest to readiest) and where they are used:

Condition 4: This is the safest of the carry conditions. In this condition, the firearm is completely unloaded. There is no cartridge in the chamber and the magazine is removed from the firearm. The hammer is lowered as well. Also, all safety devices on the firearm are turned on. In some firearm types (e.g. shotguns, rifles), the firearm may be partially disassembled as well (e.g. barrel separated from receiver), so that it will fit in a bag or case. In this condition, it will take a while to get the firearm ready to fire, because the user needs to load a magazine, insert it into the firearm, feed the first round into the firing chamber by operating the slide (which also cocks the hammer in pistols), disable all safety devices and then pull the trigger. Many people put their firearms in this condition, when they intend to store them for a long while in a gun vault (say, at the end of hunting season.)

Condition 3: In this condition, there is a loaded magazine inserted into the weapon, but there is no round in the chamber. The hammer is also down and all safety devices on the firearm are enabled. In this condition, the user needs to pull back the slide to feed the first round into the pistol's chamber (which also cocks it) and then disable all safety devices and then pull the trigger to fire. In case of a shotgun or a bolt action rifle, the user pulls on the lever to load the first round and cock the weapon.  This is the condition that many people preferred to carry single or double action revolvers in, back in the day when there were no other safety devices on them. The revolver is loaded in all chambers, except for the one that is rotated to be directly under the hammer. Any unintentional impact on the hammer will not do any harm because the chamber under the hammer is empty. When the user intends to use the revolver, they pull the hammer back first to cock it, which automatically rotates the cylinder as well and now the next chamber with a cartridge comes under the hammer, ready to be discharged.  The early Israeli weapons training in the 1940-60s also emphasized carrying firearms with no round in the chamber and hence this condition is also called the "Israeli Carry" method. The reason the Israelis taught this method is because when the new state of Israel was founded, most of its weaponry was old, second-hand goods. This meant that quite a few of their firearms had worn or malfunctioning safety devices and therefore new soldiers were taught to use condition 3 carry in order to prevent accidents. Since then, Israel has started manufacturing her own firearms and also can purchase quality firearms from other countries now, hence they no longer teach this method to new soldiers. Other people who carry in condition 3 are usually owners of older revolvers with no firing pin safety, or those who own a firearm with no external hammer (such as a Glock, Springfield XD, many pocket pistols from Browning, FN, Colt, Astra etc.) and wish to be extra safe.

Condition 2: In this condition, there is a loaded magazine inserted into the firearm and one round is loaded in the chamber already. However, the hammer is decocked. Therefore, to fire a weapon in this condition, one needs to pull the hammer back to cock it and then pull the trigger. This condition only applies to firearms with external hammers. Therefore it is not possible to carry a firearm with an internal striker (such as a Glock or a Springfield Armory XD pistol) in this condition. Also, it is recommended that the firearm have some kind of firing pin safety enabled, if carrying in this condition and preferably a decocking lever to safely decock the weapon. A double action (DA) revolver or pistol may be carried in this condition because the first pull of the trigger is much heavier (because it cocks the hammer first before firing it). Subsequent shots on a DA pistol are much easier because each shot now automatically re-cocks the pistol as well. A single action revolver with no firing pin safety (or a pistol with no firing pin safety) should never be carried in condition 2.

Condition 1: In this condition, a loaded magazine is inserted into the firearm, there is a round in the chamber and the hammer is cocked. Only the safety device(s) is enabled. This is also called the "cocked-and-locked" condition. To fire a weapon in this condition, one merely disables the safety device and then pulls the trigger. On a pistol such as a M1911, the thumb safety is enabled and the user needs to merely flick it down with the thumb and pull the trigger. This is the condition recommended for concealed carry and also recommended for use by some militaries when soldiers are travelling through a potentially hazardous zone with no visible danger apparent.

Condition 0: This is the condition where the firearm is in its most ready state. A loaded magazine is inserted into the firearm, there is a round in the chamber, the hammer is cocked and all safety devices are disabled. The user only needs to aim and pull the trigger to discharge it. This is the condition that police and soldiers carry their weapons in, if they are in a danger area with known enemies in the vicinity.

Some people consider a loaded Glock or Springfield XD pistol with no separate external safety, to be in Condition 0.5 (i.e. between conditions 0 and 1). This is because the built in safeties are enabled, but they are all connected to the trigger and once the trigger is pulled, it automatically disables all the safeties as part of the action. How this mechanism works was explained earlier in our discussion about integrated trigger safeties.

Organizations that issue M1911 style pistols usually specify the condition it is to be carried in, as part of their training doctrine.

While the carry conditions were originally written for M1911 type pistols, they generally apply to other firearms as well. While military doctrines clearly define what carry condition should be used in what situation, the same is not true in the civilian sector. Therefore, one invariably sees many arguments about which condition is best on various internet boards :).

Sunday, July 31, 2011

Safety Mechanisms: Decocking Lever

In this post, we will study a safety feature that is present in some semi-automatic pistols that are Double Action. Recall in our discussion about revolvers that double action firearms are generally able to operate in double action as well as single action mode (unless they are labelled DAO - Double Action Only, in which case they only operate in double action mode). In pistols of this sort, the user may manually pull back the hammer to cock it and then pull the trigger to release it (single action mode), or simply pull the trigger back, which cocks the hammer and then releases it (double action mode).

When fired in double action mode, the trigger pull is harder and longer since the trigger action needs to cock the hammer before releasing it.

In many cases, people like to carry their pistols with one round chambered, but the hammer decocked and any other safety devices may be turned on or off. The pistol is "considered safe" because it takes a longer and stronger trigger pull to cock and release the hammer, than if the hammer was cocked already and the trigger merely releases it.

So when a user wants to carry a pistol in this state, they initially insert a loaded magazine normally and then pull back on the pistol's slide to load the first round in the chamber. However, this same action also cocks the hammer. So, now the user wants to decock the hammer without firing the pistol. In olden days, the trick was to hold the hammer's spur down with the thumb and then pull on the trigger and then slowly let down the hammer so that it falls back to the "safe" position without discharging the loaded cartridge. Of course, this approach has some danger in that if the user's thumb slips off the hammer's spur, it could cause the hammer to strike the cartridge with force and discharge it. In order to reduce this danger, a decocking lever was introduced.

With a decocking lever, the mechanism either blocks the hammer from slamming on the firing mechanism, or by covering or retracting the firing pin out of the way, so that the hammer can be safely released without triggering the firearm. Of course, all mechanisms can fail, so it is still a good idea to point the firearm in a safe direction before operating the decocker lever.

Decocking mechanisms are found on pistols from many manufacturers: Heckler & Koch, the Sig Sauer pistol family, Walther pistols etc.

Thursday, July 28, 2011

Safety Mechanisms: Drop Safety

In our last post, we studied a Glock pistol for its integrated trigger safety, but we also noted that the Glock feature two additional safeties, that guard against discharge if the firearm is accidentally dropped. We will study more about those mechanisms in this post.

Mechanisms that prevent the firearm from going off when dropped or roughly handled, fall under the class of Drop Safety. These safeties work by providing an obstruction between the firing mechanism and the cartridge and are connected to the trigger. As the trigger is being pulled, these safety devices are deactivated one after other with the trigger movement. Therefore, if the firearm is accidentally dropped, the drop safety devices are all active since no one is pulling the trigger. Hopefully they work and therefore stop the firearm from going off accidentally.

The first drop safety we will study is something we mentioned in the previous article, a firing pin block safety. This is a mechanism that sits in the path between the firing pin and the cartridge primer and prevents the firing pin from striking the cartridge, when it is active. The firing pin block is connected to the trigger and as the trigger is pulled back, the firing pin block moves out the path between the firing pin and cartridge, just before the hammer is released. The hammer then strikes the back of the firing pin and the front of the firing pin can now freely strike the base of the cartridge, since the firing pin block is now out of the way. When the trigger is released, the firing pin block moves back into place again and blocks the firing pin from striking the cartridge.

The next drop safety mechanism we will study is the hammer block. The concept is very similar to the firing pin block, except that in the case of the hammer block, the mechanism sits in between the hammer and the back of the firing pin. So when it is active, the hammer cannot strike the back of the firing pin. Like the firing pin block safety, this mechanism is also connected to the trigger and the hammer block moves out of the way as the trigger is pulled.

The next drop safety mechanism we will study is the transfer bar, which is used in revolvers. In this case, the hammer does not directly strike the cartridge. Instead, there is a transfer bar that has a firing pin attached on the other end, which contacts the cartridge. When the firearm is not in use, the transfer bar is moved out of the way between the hammer and the cartridge (which is the opposite of the other mechanisms we have seen so far.). So if the firearm is dropped accidentally and the hammer releases due to impact, the hammer still won't contact the cartridge When the trigger is pulled, the transfer bar is moved into position just before the hammer is released. The hammer now strikes the transfer bar and the other end of the transfer bar which is connected to the firing pin then strikes the cartridge and discharges the firearm.

The last drop safety mechanism we will study is the oldest one: the safety notch. Unlike all the others that we've studied so far, this is a feature that needs to be engaged by the user manually. This type is used by old revolvers, lever action rifles, some old semi-automatic pistols etc. The safety notch is a cut made to the tumbler and connected to the hammer. If it is engaged, the hammer is caught before it can strike the firing pin. Therefore, if the weapon was fully cocked and if the safety was turned on, even if an accidental drop releases the hammer, it is caught at a half-cocked point by the safety mechanism.

In many areas, the law now requires that all new firearms have at least one form of  drop safety on them. Many pistols have more than one drop safety mechanism, so that if one of them is worn out, one of the others will hopefully work and prevent the pistol from accidentally discharging.

Wednesday, July 27, 2011

Safety Mechanisms: Integrated Trigger Safety

In our last post, we looked at Grip Safety Devices. In this post, we will look at something similar, the Integrated Trigger Safety device. This device really became popular because of Glock pistols, and other manufacturers such as Springfield Armory and Smith & Wesson also offer some models with this feature.

 Public domain image. Click on image to enlarge.

The above image shows a typical Glock 17 Generation 2 pistol. If you were to click on the image to enlarge it, pay attention to the trigger assembly and notice that it seems a little thicker towards the bottom. That is because the trigger has a small spring loaded lever embedded into the lower half of the trigger. This is the integrated trigger safety device.

Similar to the grip safety, this spring loaded lever is automatically depressed by the user as a natural consequence of the user's actions, in this case, pulling the trigger. When the lever is depressed, it unlocks the main trigger and allows it to move. One cannot move the main trigger without depressing the small lever fully.

There are two additional safety devices built into Glock pistol models, which are also activated and deactivated by the trigger movement. One of these devices is a drop safety device. This guides the trigger bar in a ramp and it only releases by the rear-ward movement of the trigger. The other device is a firing pin safety, which is a small steel pin that sits in between the firing pin and the cartridge. The firing pin cannot strike the cartridge primer with the steel pin in the way. This steel firing pin safety device only drops out of the way, when the trigger is pulled. These devices get deactivated as a natural consequence of the trigger being pulled and are reactivated when the trigger is released.

Therefore, if the user were to drop the pistol accidentally, the safety devices would automatically activate and hopefully prevent the firearm from discharging. This design found widespread popularity among many users, who prefer not to move any manual lever or button to activate and deactivate the safety. The firearm still goes bang when the user pulls the trigger, but not if it were to be accidentally dropped.

Since Glock pistols became very popular, some other manufacturers took notice and used a similar feature in some of their products.

Sunday, July 24, 2011

Safety Mechanisms: Grip safety

In the last couple of posts, we studied the basics of firearm safety mechanisms as well as some manual safety mechanisms. In this post, we will study a particular type of safety mechanism called the Grip Safety. This is a popular mechanism that was first seen on the classic John Browning designed Colt M1911 pistol and later seen on other pistol models as well. It is also found in the Israeli Uzi submachine gun.

Like the name implies, a grip safety device is a lever located in the grip of the firearm. The user's hand naturally depresses the safety lever when he or she grips the firearm and this disables the safety device, thus enabling the user to pull the trigger and operate the firearm. When the user releases their grip on the firearm, the safety lever automatically pops out again and is re-enabled.

Public domain image. Click on image to enlarge.

The above image shows a Colt M1911A1 pistol. The grip safety lever is at the back of the hand grip and is automatically depressed when the user holds the pistol. There is also a manual safety lever on the firearm, at the rear of the slide, which you ought to be able to spot easily, if you've read the previous post.

Believe it or not, the original John Browning design didn't actually have a safety device, but the US Army insisted on adding a grip safety and a manual safety for the original M1911 pistol design, before they would accept it.  Hence, John Browning added them for the M1911, which stayed in service from 1911-1924. The changes made to the M1911A1 model (which has been manufactured from 1924 to the present day) were relatively minor: Longer grip, wider front sight, shorter spur on the hammer etc., so it still has a grip safety and manual safety.

Public domain image. Click on image to enlarge.

The firearm depicted above is the Israeli made Uzi submachine gun. The grip safety is labelled in the above image and is pretty easy to see.

The nice thing about this design is that it is automatically enabled or disabled as the user holds or releases the firearm's grips. Therefore, a firearm with this safety device will only fire if the user is actually holding the firearm and intending to discharge it. Thus, if the user were to accidentally drop the firearm, the safety automatically enables and prevents the firearm from discharging accidentally.

Safety Mechanisms: Manual Safeties

In our last post, we saw some of the basic types of firearms safety mechanisms. We will now study one type, the manual or external safety.

When set to the "safe" position, such mechanisms either prevent the trigger from moving or prevent the firing mechanism from moving or disconnect the trigger from the firing mechanism (or a combination of any of the above). Since these mechanisms typically fiddle with the working of the firearm action, the levers or buttons to activate/deactivate them are typically found close to the action as well.

There are various types of these manual safeties, such as sliding lever safety, cross bolt safety (a.k.a button safety), thumb safety etc. We will look at some of these types below.

Sliding safety or Tang safety

In the above image, we see a sliding safety lever. The lever A is a rotating lever that is rotated to lock or release the barrels from the closed state. However, lever A is not the safety. If you look behind the lever A, there is a sliding switch B, which is the safety. When set to safe, the trigger cannot be pulled.

Cross bolt or Button safety

The next type of safety is typically seen in rifles and shotguns. It is a cross-bolt or button safety. The safety is the large button labelled A right behind the trigger in the image above. When the safety is activated, it prevents the trigger from moving.

Safety/Selector lever on an AK. Click on image to enlarge.

The above image shows a selector switch/safety of an AK type firearm. The long selector lever is labelled as A in the image above. When the lever is rotated to the safe position, as in the image above, it not only locks the trigger, but also physically prevents the bolt from moving backwards fully. When rotated to either the single shot or auto-fire mode, the bolt is free to move backwards all the way

Pivot Safety

The next type of safety we will look at is the Pivot safety, where the safety lever moves about a pivot point. The above particular example also falls under the class of "thumb safety". These are typically manipulated by using the thumb to manipulate the lever, hence the name. In the above image, the lever labelled A is the pivot safety. These are common on many pistols. They work by preventing the hammer from striking the firing pin and many also disengage the trigger from the rest of the action. Some of them also serve as decocking levers, i.e. the hammer may be dropped safely so that the weapon is no longer cocked. In many pistols, there is also a corresponding lever on the other side of the slide, so that the safety can be manipulated equally easily by either a left-handed or right-handed shooter.

Click on image to enlarge.

In the above example, we see another "thumb safety" type on the pistol, but this one is a sliding button type. You can see the button directly under the red dot on the slide. Like the other thumb safety we saw above, this pistol also has another button on the other side as well, so it can be used by left or right handed shooters. Actually, this pistol has two other safety mechanisms as well, a trigger safety (note the double-trigger mechanism, the first one is a trigger safety) and a grip safety as well. We will discuss these safeties in later posts.

It must be remembered that preventing the trigger from moving only is sometimes not enough to ensure safety, as a sudden blow to the firearm in the right spot can still release the firing mechanism. Hence it is better to have a mechanism that prevents the firing mechanism from moving as well.

Tuesday, July 19, 2011

Safety Mechanisms

In the next series of blog posts, we will look into a very important topic: firearms safety mechanisms. So what is a firearms safety mechanism and why do we need them? Well, a firearm is a weapon and we do not wish to use a firearm unless absolutely necessary, for obvious reasons. Therefore, there must be some mechanism or mechanisms that protect a firearm from accidental discharge, for example, if it were to be accidentally dropped, or if the firearm was hit by a rock or a ball or some such flying object.

The first way to do this is to carry a firearm in such a manner that it is loaded, but the user must perform an additional action before the firearm can be discharged. For example, with revolvers, people generally carry them with all but one of the chambers loaded. The lone chamber that is left unloaded is then rotated so that it is directly under the hammer and the revolver is also left uncocked. So, if the revolver were a six-shooter, the user loads five out of six chambers in the cylinder and then rotates the cylinder so that the empty chamber is the one that the revolver's hammer is directly pointing at. Therefore, if the hammer is accidentally struck, it only falls on an empty chamber. To deliberately discharge the firearm, the user needs to pull the hammer back fully with his thumb (assuming a single action revolver), which cocks the hammer and also rotates the cylinder so that the hammer will now fall on a loaded chamber. For a double action revolver, the user pulls back the trigger fully. Since it is acting in double action mode, the revolver trigger pull is much heavier and the trigger pull simultaneously cocks the hammer, rotates the cylinder to the next chamber and then releases the hammer. While this technique is actually a "policy", not a "mechanism", on many revolvers (especially older ones), this is often the only "safety mechanism" that users have.

Similarly, for modern pistols, shotguns and semi-automatic and automatic rifles, users may simply fill the magazine with cartridges and load it in, but carry the firearm without a cartridge in the firing chamber. To discharge the firearm, the user needs to hold the firearm with one hand and use the other hand to pull back on the slide (or lever in case of some shotguns or rifles) to cock the weapon and also load the first cartridge from the magazine into the firing chamber. Then the user can pull the trigger to discharge the firearm. Therefore, it takes a conscious pair of actions before the firearm is made ready to fire and it cannot be discharged unintentionally, if say, it were accidentally dropped on the hammer. This method is sometimes called the "Israeli Carry" method in the US and Canada. The origin of this term is because in the early days of the IDF (Israeli Defense Force) history, they had severe budget constraints and were forced to acquire large numbers of antiquated firearms with questionable mechanical safety mechanisms. Therefore, the early IDF personnel were taught to carry with the chamber empty and hammer down.

Of course, quite a few people like to carry their firearms loaded and cocked, with one cartridge already in the chamber (called the "+1 carry method" i.e. magazine fully loaded + 1 extra loaded in the chamber), because they do not like the idea of spending extra time to prepare the weapon for firing, which may cost one's life.  Also, there may be a chance that the user may drop the weapon after they have begun firing. Obviously, there needs to be safety mechanisms to protect against these situations as well. These are the mechanical safety mechanisms we will study in the next few posts.

Safeties can be divided into two major types:

  1. External or manual safety: These typically consist of mechanisms which explicitly require the user to switch them on or off separately. For example, there may be a safety lever or button that needs to be pushed to turn the safety mechanism off.
  2. Internal or automatic safety: These are typically turned on or off as part of another action. For instance, many modern firearms have a hammer block that prevents the hammer from striking the firing pin. Only when the trigger is pulled is the hammer block moved out of the way of the hammer's path. Therefore, the act of pulling the trigger deactivates the internal safety and the hammer will not strike the firing pin if the firearm is accidentally dropped.
Many modern firearms come with a mixture of both types of safeties. We will look into various safety mechanisms in the next few posts.

As might be noted, the argument about carrying a firearm with the chamber loaded or not is an ongoing one. Some argue that it takes too long to load a cartridge into the chamber, while others say it doesn't take that much extra time. Others argue that in a stressful situation, one may forget to load the weapon. Also the user may not have both hands free to do this. These days, with access to better firearms, the Israelis have even stopped teaching the so-called "Israeli carry" method for the last 20 years or so. The following pair of videos shows both techniques:

Friday, July 8, 2011

Night Vision Devices

In this post, we will look into a special form of sights, the Night Vision Device. These allow the user to operate in darkness and low light conditions.

The origin of night vision devices traces back to a bit before World War II broke out. The American RCA company and the German company AEG Telefunken were the pioneers in this field in the mid-1930s. The first generation of these devices (often referred to as "Generation-0") were of the "active" type. What this means is that these devices work by projecting infrared light upon a target and then making an image intensifier that is sensitive to light at these frequencies. The image intensifier uses a vacuum tube to accelerate electrons reflected from the IR beam on the target, between the anode and photo cathode of the tube. The accelerated energy charge strikes a phosphor screen (like a TV screen) where the image is focused and can be viewed via an eyepiece. Since human beings cannot see infrared light, they are unaware that they are being targeted in the dark. The first such devices were designed to be used by snipers. Many of these Gen-0 devices had pretty abysmal sensitivity and were sometimes worse than an unaided human eye. Another major problem with these devices was that the enemy troops could also wear night vision goggles and immediately detect where the sniper was hiding. The image intensifiers used vacuum tube technology and therefore, used large amounts of electricity. The use of vacuum tubes also distorted the returned images quite a lot. Vacuum tubes also had a shorter life and would often stop working in the field. The infrared illuminators were also pretty massive and often had to be mounted to a flat-bed truck. Despite these disadvantages, Gen-0 devices saw use in World War II and the Korean conflict.

The next generation devices ("Gen-1") saw action during the Vietnam War in the 1960s. Unlike Gen-0 devices, these were designed to be "passive" type devices (i.e.) they do not require their own source of infrared light and can work under moonlight conditions.

Generation 1 Night Vision Device AN/PVS-2 mounted on M16 assault rifle. Click on image to enlarge. Public domain image.

In the above image, we see a typical Generation 1 device from the Vietnam war era, mounted on top of an M16 A1 rifle. The device in question in an AN/PVS-2 Starlight scope. The device is still pretty bulky, but it doesn't need a separate IR projector. The image intensifier technology still used vacuum tube technology and still had image distortion problems. To improve the gain on these devices, multiple vacuum tubes were often cascaded together, making the image amplification to the order of 1000x to 2000x and having a service life of around 2000 hours. Despite that, these devices only worked well during full moon conditions and could not be used in anything less than half-moon conditions, which means they were pretty much useless during half the month and also on cloudy nights.

The next generation of devices ("Generation 2") came out in the 1970s. Due to major improvements in tube technology, Generation 2 devices offer much less distortion of the image and more reliability than Generation 1 devices. Gen-2 devices use microchannel plates instead of cascading vacuum tubes in the image intensifier. This makes them much more sensitive to IR light than Gen-1 devices and they can be used effectively even on moonless nights and in fog and cloudy conditions. The use of microchannel plates means that the viewed image often has a distinct square or hexagonal pattern on it.  Compared to Gen-1 devices, these typically offer up to 20,000x to 30,000x amplification and last about 2500 to 4000 hours. Examples of such devices include the AN/PVS-4 and AN/PVS-5.

A soldier using an AN/PVS-4 night vision device.

Gen-2 was followed by an improved Gen-2+, which offers better performance during high and low light levels. In fact, Gen-2 devices may still be found on sale in the market today.

The next generation (Generation-3) of devices has no change in the basic technology of Generation 2 devices, but the components themselves have improved, thereby contributing to better resolution and longer life. For one thing, the photo cathode uses Gallium Arsenide (GaAs), which makes it much more efficient than the older technologies. The microchannel plate is also coated with an ion barrier film, thereby increasing the life of the device. Gen-3 devices offer 30,000x to 50,000x amplification and  last about 10,000 hours or so. The first Gen-3 device was the AN/PVS-7 which was originally fielded in limited numbers in 1988 to military personnel in Fort Hood. This was followed by AN/PVS-10 and AN/PVS-14 in the 1990s and Gen-3 devices are still in use with the US military. In fact, they saw widespread use in Operation Desert Storm in the 1990s, where they certainly proved their worth.

During all this time, night vision devices were mainly used by military forces because of high prices and lack of accessibility in the civilian market. That all changed during the early 1990s, due to the collapse of the former Soviet Union. A number of Gen-0 and Gen-1 devices from Soviet military surplus became available in the western civilian market and caused an overall drop in the prices of night vision devices and they became much more accessible to civilians as well. These days, one may find Gen 2, Gen 2+ and Gen 3 devices available for sale to civilians.

Generation-4 devices are currently under development. Among the planned improvements is an automatic gated power system, which allows quick switching on and off of the photo cathode. This allows the user to move from a well lit to a dark environment or vice-versa easily.

One question that puzzles many people is why does the image of a night vision device show up in green? There is actually a very good reason for this. Apparently, the phosphor screen is deliberately coated green because it turns out that the human eye can distinguish between more shades of green than any other color.

Thursday, July 7, 2011

Flash Suppressor a.k.a Flash Hider

In our last couple of posts, we studied the topic of suppressors (a.k.a. silencers). In this post, we will study a related family of devices, the flash suppressor a.k.a flash hider. In our study of silencers, the main purpose of those is to reduce the sound level of the firearm to make it more comfortable for the user to use it. As was noted previously, many silencers also reduce the amount of flash coming out of the weapon as well.

A flash suppressor (a.k.a) flash hider is not designed to remove any sound from the firearm. Instead, its sole purpose is to reduce the flash from the muzzle. So what is muzzle flash and why do we need to get rid of it. Basically, when a firearm is fired, the cartridge propellant burns inside the barrel and pushes the bullet out. If the barrel is a little too short or if the quantity of propellant is a bit too much, some of the propellant particles end up burning outside the barrel and thereby creating a huge fireball in front of the gun. The sudden bright flash may cause the user to be temporarily blinded, especially during night time. This was not so much a problem in previous centuries, when firearms had really long barrels and propellants had plenty of time to burn completely inside the barrel. With newer powders and modern assault rifles having much shorter barrels than previous firearms, it became much more of a common occurrence. Carbines also experience this problem due to having shorter barrels than normal rifles.

A flash suppressor works in a couple of ways. First, it can redirect the exiting gases to exit via the sides of the barrel instead of in all directions, thereby keeping the shooter's vision at the top of the barrel unaffected. Second, it allows the exiting gases to expand rapidly, which cools them off and reduces their temperature, which also reduces or eliminates the brightness of the flash.

The earliest type of flash suppressor came out around World War II and is called the cone suppressor or cone flash hider. This was introduced with the Lee Enfield carbine model V. They may still be seen these days on some AK models.
A cone flash suppressor which is normally used with AKs

An AK weapon with attached cone flash hider

In the above pictures, we see a shortened AKS-74 with a cone style flash hider. It is a screw on type, which may be attached to the end of an appropriately threaded barrel. Note the hole on top in the first picture. When screwed on, this hole serves to redirect some gases up and acts as a brake to reduce the muzzle climb as well.

The next type of flash hider we will study is the duckbill type, which was often seen on early M16 models used in Vietnam. This consists of a device with a number of prongs on it, such as the image below:

A duckbill type flash suppressor

Early M16 A1 model with duckbill flash suppressor attached. Click on image to enlarge.

As can be seen by the image above, the flattened prongs tend to resemble the bill (beak) of a duck, which gives this device its name. The prongs serve to redirect the gases to the sides, but not to the top of the barrel, so any flash that is generated will not go in that direction. While these were more effective than the earlier cone models, the prongs tended to get fouled up with vegetation when fighting in the jungle. The prongs also have a chance of getting bent on the open end, due to rough usage in the field. This doesn't mean that open-type flash hiders like this are obsolete. Some modern weapons, such as the Heckler & Koch G36 series still use them.

The problems experienced with the duckbill type flash suppressor led to the development of the birdcage type of flash suppressor. This is similar to the duckbill type, but also has a ring in front of the flash suppressor.

Birdcage type flash suppressor.

The ring in front supports the prongs and also prevents branches, grass and other vegetation from easily entering into the prongs. This type of flash suppressor came standard with the M16 A2 model. Also, in the M16A2, the flash suppressor not only prevents gas escaping from the top, the bottom is closed off as well. This prevents the hot gases from kicking up sand and dust when the shooter is firing from the prone position. This type is seen on many weapons today , including AKs, SIG, M16 etc.

Sunday, July 3, 2011

Suppressors a.k.a Silencers - Part II

In our previous post, we studied some basics of suppressor technology. We will now study them in a bit more detail.

As we noted in the previous post, the way that suppressors work is by slowing the expanding propellant gases by trapping them in chambers and allowing them to expand and cool a bit, which causes them to escape out of the muzzle at a lower pressure and velocity than if the suppressor was not present.

There are two basic types of suppressor (a) the screw-on type (a.k.a can type or muzzle type), where a suppressor is simply screwed on to the end of the muzzle when required and (b) the integral type (a.k.a Reflex suppressor), where the suppressor is designed as part of the barrel. The screw-on type suppressor is often  a third party attachment and not designed by the manufacturer of the firearm. It can be screwed-on or removed as desired by the user and can also be used on other firearms as well, provided they are all of the same or smaller caliber. Firearms typically need to be modified to add a screw thread on the outside of the barrel in order to screw on the screw-on type suppressor. Contrast this with the integral type suppressor, which is designed by the firearm manufacturer from the very beginning as part of the firearm. With this type, the barrel is enclosed by the suppressor along its length and the barrel is drilled in several places to allow the expanding propellant gases to bleed off into the enclosing suppressor. Since the integral suppressor encloses the barrel, this makes the overall weapon length shorter than if one was using a can-type suppressor.

Even though suppressors work by slowing down the exit gases, well designed ones do not affect the exit velocity of the bullet that much. In addition, many of them also reduce the flash and recoil of the firearm as well. The expanding gases do contribute to wear and tear on the internals of the suppressor. Depending on the type and materials used in constructing the device, the wear rates can greatly vary. Cheap ones can last between 15-20 shots, whereas a good one could easily last 30,000 shots or so.

Sunday, May 29, 2011

Suppressors a.k.a Silencers - Part I

A suppressor (or a "silencer") is a device that is screwed on to the barrel of a gun and designed to reduce the amount of noise and flash generated by a weapon. Before we start to study about these devices, it is good to clear up a few myths about them (and these myths are mainly due to Hollywood movies). The biggest myth is that they make a firearm almost noiseless -- you only hear a soft "phut" noise, if all the James Bond movies are to be believed. The second biggest myth is that in the absence of a suppressor, you can improvise with almost any cylindrical object (bottle filled with water, coke can etc.)

The first thing to note is that there are multiple sources of noise possible from a firearm:
  1. Noise of the hammer striking the cartridge.
  2. Noise due to the exploding propellant material and hot gases leaving the barrel.
  3. Noise due to the bullet flying through the air (sonic boom, if the bullet is flying supersonic).
  4. Noise due to ejecting the empty cartridge case and cocking the weapon.
  5. Noise due to bullet striking the target.
Of all these sources, #2 and #3 are the main sources of loud noise from a firearm. Let us consider the noise from #2 (i.e. exploding propellant material). This typically hits about 140-160 dB, which is louder than your average heavy metal concert (trust me on this one, I've attended quite a few of them). No suppressor is going to remove such a loud noise like this completely. At the most, a suppressor drops the sound level to around 130-145 dB, with the quietest ones measuring about 117 dB, which is still in heavy metal concert territory. So, what's the use of such a device if it doesn't remove the sound completely. Well, when hearing protection is added, this makes the loudness level easier to bear. These devices also remove the flash emanating from the barrel and thus make it less likely to disorient shooters. They also change the sound signature of a firearm, so that the sound doesn't exactly sound like a shot. As the old Finnish expression goes, "A silencer does not make a marksman silent, but it makes him invisible".  You can observe how the sound signature changes in the below video, where the person fires a 9 mm. pistol, first with no suppressor and then with a suppressor screwed on:

As you may note, the suppressor doesn't completely remove all the noise, but it does remove a fair amount and also the sound no longer sounds like a gunshot.

There were many inventors of silencing devices towards the end of the 19th century, with one patent granted to J. Borrensen and S. Sigbjornsen for a device that "lessens the sound of discharge" in 1899. However, the earliest successful commercial suppressor was invented in 1908 by the American inventor, Hiram Percy Maxim, the son of Sir Hiram Stevens Maxim, the man who invented the first portable automatic machine gun. His device consists of a hollow cylindrical tube with a number of expansion chambers in it.

This device is screwed on to the end of the barrel. Expanding gases from firing the cartridge are trapped by the baffle plates, while the bullet travels through the hole in the center. The trapped gases expand and cool and thereby exit out of the barrel with less pressure and velocity, which reduces the noise. This device was sold under the trademarked name "Maxim Silencer", which is probably why we still call suppressor devices as "silencers" even though they don't actually silence a firearm completely.

Mr. Hiram P. Maxim also had interests in the emerging automobile industry and he developed a similar device to reduce engine noise, which we still use today: the muffler, which is also known as a "silencer" in some parts of Asia and Europe.

Since these devices don't entirely remove the noise, the firearms industry prefers to call them "suppressors" instead of "silencers". In our next post, we will look into more about such devices.

What is a wildcat cartridge?

A wildcat cartridge is a custom made cartridge, usually made by modifying an existing commercial cartridge, in order to optimize cartridge performance (e.g. more power, more velocity, better accuracy etc.) Since these are custom made, they are more expensive than normal cartridges. Also, wildcat cartridges are usually used mainly by very serious shooters and hand-loading fans, there is only a limited market for them and larger cartridge manufacturers generally don't make them.

In terms of variety, there are more wildcat cartridge varieties than commercial production cartridges. However, many of these varieties are produced in very small quantities indeed.

In some cases though, some cartridges started out as custom-made wildcat cartridges, but gained enough popularity that they began to be commercialized (i.e. rifles chambered for them are now available commercially) and SAAMI standards were specified for them. Examples of such cartridges are the 6.8 mm. SPC, which was originally developed in collaboration with some members of US SOCOM. The 6.8 mm SPC is based on a .30 Remington cartridge, modified to .270 caliber and then further modified in length to fit in an magazine that can be fitted into the magazine wells of the M16 rifle. Therefore, any M16 or AR15 type rifle only needs replacing of the barrel, bolt and magazine to use this new cartridge. This cartridge is more lethal than the standard NATO 5.56x45 mm. cartridge fired by the M16 and while it is not officially adopted by the military, it has found use by special forces troops in Afghanistan and Iraq and is gaining popularity as a commercial civilian round. Another example is the well-known .357 magnum cartridge developed by Smith & Wesson, which was originally developed from a .38 Special cartridge. The .357 and .38 Special cartridge are both the same diameter externally and only differ slightly in length, because of safety reasons. Early versions of .357 magnum were actually identical dimensions to .38 special cartridges and the length was only altered so that people could not accidentally load the more powerful .357 magnum cartridges into a firearm not designed for the additional pressure. Another example is the 6 mm. PPC (Palmisano & Pindel Cartridge, named after its inventors, Lou Palmisano and Ferris Pindell). This cartridge started out as an improvement of the .220 Russian cartridge, which was itself based on the venerable 7.62x39 mm. cartridge used on the AK-47 and AKM assault rifles. The 6 mm. PPC case is made by forming the .220 Russian brass case into a new shape and is specially geared for single-shot bench rest shooting. It is one of the most accurate cartridges available up to 300 yard ranges and has been produced since 1975 and used in several competitions.

As mentioned earlier, wildcat cartridges are generally used by very serious shooters mainly and quite a few require barrel modifications also in order to use the modified cartridge. The modified barrels are usually supplied by custom barrel makers, who typically work out of small shops. The custom barrel makers generally also supply the buyer with reloading tools and dies, so that buyers can make their own cartridges. Some barrel makers also supply data about how different powder brands, powder quantities and bullet weights perform with their barrels. Therefore, most wildcat cartridges are developed, either by the custom barrel makers themselves, or by someone who is working in conjunction with a custom barrel maker.

.243 Winchester Ackley Improved wildcat cartridge on the left, compared to a normal .243 Winchester cartridge on the right.
Note the reduced case taper and sharper shoulder angle in the Ackley Improved version, which leads to more case capacity and therefore, more propellant.
Image copyright Arthurh at wikipedia and licensed under the Creative Commons Attribution-Share Alike 3.0 Unported License. 

There are many reasons why people develop wildcat cartridges, such as:

  • Increasing the case capacity (as in the Ackley Improved cartridge pictured above) allows adding more propellant to the cartridge, which increases the velocity of the bullet and therefore, the energy transferred by the bullet.
  • Reducing the bullet's caliber increases its velocity, thereby increasing its resistance to wind drift.
  • Better consistency can be achieved by tuning a bullet's diameter, weight and velocity to a particular amount and type of propellant, which leads to greater accuracy.
  • Feeding issues of certain types of ammunition can be fixed. For instance, it is not possible to reliably fire hollow-point bullets with .45 ACP pistol ammunition because of feeding issues from the magazine. Hence, the shape of the cylindrical cased .45 ACP cartridge was modified to a bottlenecked .45 cartridge to solve this issue.
  • Some shooters like to use rifle ammunition with pistols, for greater accuracy. In this case, one starts out with a rifle cartridge and then reduces its case capacity so that it can be used with a pistol.
A wildcat manufacturer generally starts out by using a commercial cartridge case and changing its shape to new dimensions. Usually, this involves pushing the shoulder of the cartridge backwards or forwards as needed to modify the case capacity and also changing the diameter and length of the cartridge neck. This process can be done by either cold forming (i.e. the case is pushed into a die and pressure is applied to change the shape of the case) or fire forming (i.e. the case is placed in a chamber of a different dimension and loaded with a light gunpowder charge. Upon firing the charge, the case takes the shape of the new chamber). Sometimes a mixture of both methods is used to make the final case shape of a wildcat cartridge. Next, the manufacturer trims the case to the appropriate length, because cold forming or fire forming generally tends to increase the length of the case's mouth and the excess length needs to be trimmed. Then the diameter of the neck is changed as needed for the new bullet. The cartridge is then hand-loaded carefully and a bullet is crimped on.

In quite a few situations, firearms can be very easily modified to use the new wildcat cartridges. For example, the Ackley Improved cartridge shown above could easily be used by rechambering an existing firearm. Better still, a firearm that is chambered for the "Improved" cartridge can also fire standard factory loaded ammunition as well, which allows the owner to use less expensive and commonly available ammunition if there is a shortage of wildcat cartridges. Ackley Improved family of cartridges were developed by Patrick Otto Ackley, a prolific gunsmith and author, who produced many improved versions of commercial cartridges in several different calibers.

History and Development of the Assault Rifle - X

With the advent of bullpup designs in the 1970s such as the Austrian Steyr AUG and the French FAMAS, some of the newer designs that have emerged since then have largely been bullpup designs. Some of these include the British L85A1 and L85A2 of the 1980s, the Chinese QBZ-95, the German Heckler & Koch G11, Singapore's SAR-21, Israel's Tavor TAR-21 etc.

Since the advent of the 5.56x45 mm. NATO cartridge, the world has essentially gone into three basic calibers as far as militaries are concerned: the NATO 5.56x45 mm. (used by M16, Steyr AUG, FAMAS, L85, INSAS etc.), the Russian 5.45x39 mm. (used by AK74 family) and the Russian 7.62x39 mm. (used by AK-47, AKM and clones such as the Type 56). The first two of these are generally used by most military forces, whereas the third cartridge is generally widespread among many insurgent groups due to the popularity and wide-spread nature of the AK-47 and AKM family of assault rifles. However, there has been some other significant research in cartridge developments as well. Both the UK and the US did some work to find an intermediate cartridge between the NATO 5.56x45 mm. and the older NATO 7.62x51 mm., in order to strike a balance between bullet effectiveness and recoil force. This was due to the 7.62x51 mm. cartridge having too much power and weight and the 5.56x45 mm. not having sufficient range for some applications. Experiments showed that cartridges such as the 6x45 mm., the Grendel 6.5x38 mm. or the Remington SPC 6.8x43 mm. strike a pretty good balance by having more range than a 5.56x45 mm. cartridge, but still having relatively less recoil and less weight than a 7.62x51 mm. cartridge. With combat in Afghanistan taking place over longer ranges and the advent of scopes on assault rifles, it is possible for an infantryman to engage over longer ranges now and hence there have been noises made in various quarters to replace the M16 with a newer rifle using one of these cartridges instead.

Newer bullet designs using exotic technologies were also tried out during the 1970s and 80s, but they've been much less successful in this regard. For instance, there were attempts to design cartridges that fired flechette darts instead of conventional bullets. However, the cost of ammunition was prohibitive and thus this never became popular. Another exotic concept was folded ammunition, which was ammunition that was roughly U-shaped. The idea was to reduce the length of the cartridge in order to speed up the firing cycle of rifles.

Folded ammunition examples. Click on images to enlarge.

Folding ammunition never caught on either. Another concept was the caseless ammunition cartridge, for which a lot of work was done by Hecker & Koch and Dynamit industries. The idea is that since a caseless cartridge doesn't have a brass case, there is no need for the rifle to eject it after every shot, which reduces the number of steps in a firing cycle and thereby enables faster firing rates. H&K developed the G11 assault rifle to use caseless ammunition. The concept of a consumable cartridge is actually a very old one, as it was used by the Dreyse Needle Gun of 1835! However, with automatic weapons and modern ammunition, there are more problems to solve. For one, caseless cartridges are more easily damaged by rough handling since they don't have a hard outer case and two, the brass case removes some of the heat from the chamber of the firearm and the lack of a brass case means that caseless ammunition could cook-off in a hot chamber. H&K solved the first problem by putting cartridges in a sealed plastic case and had to spend a lot of time developing special propellants to solve the second issue. The G11 was about to be adopted by the West German military when the Berlin wall came down and the cold war ended. This resulted in cutbacks in military spending and H&K went into financial difficulties as a result and was acquired by the British, where they earned their keep by helping fix problems with the British L85 assault rifles. Interest in caseless ammunition technology has been renewed since 2004, due to the US military's Lightweight Small Arms Technology (LSAT) program.

Oddly enough, despite most of the new rifles being bullpup layouts, the US military is looking at conventional layouts for their M16 replacements. For instance, the US Army has switched to the M4 (which is the carbine form of the M16). The (now cancelled) XM8 project, which was designed to replace the M16, also had a conventional layout:
XM8 Assault Rifle. Click on image to enlarge. Public domain image.

The FN SCAR, adopted by the US Special Operations Command (SOCOM) as well as the US Marines M27 Infantry Automatic Rifle also use conventional layouts. Thus, it appears that the US is definitely not bucking the bullpup-layout trend, at least in the near future.

Another interesting concept developed in Australia is the Metal Storm rifle, where many bullets are stacked head to tail in series inside a barrel, with propellant between the bullets. Ignition of individual cartridges is accomplished electronically. Since the cartridges are completely consumable and because they are stacked one behind the other in line, there is no need for case ejection or a feed system to load new cartridges in the chamber. This makes the firing rate much faster than other designs, as well as contributing to reduced weight. As of now, Metal Storm products have found limited use and support from the US Marines.