Sunday, June 29, 2014

Helical Magazines

In our last article, we studied the rotary magazine. In today's article, we will study a magazine that was invented more recently. Today's object of study will be the helical magazine.

The helical magazine was invented by Michael Miller and Warren Stockton in 1985 and produced by the California Instrumentation Company (later known as "Calico"). Interestingly, the California Instrumentation Company was originally known for manufacturing specialized instrumentation for the petroleum industry, but since they already had experience in tooling and engineering, they didn't have too much trouble manufacturing firearms. By about 1988 or 1989, they had the bugs ironed out and started producing them in quantity, along with firearms designed to use these magazines.

Image from the patent application for the helical magazine. Click on the image to enlarge. Public domain image.

The concept behind the helical magazine is to arrange the cartridges in a helical spiral, as shown by figure 2 above. A drive spring rotates the drive member and pushes the cartridges into the chamber. The figure below shows a cutaway of how the magazine works:

Cutaway of a helical magazine on a Calico firearm. Click on the image to enlarge.

The full patent details for this type of magazine may be viewed here. The nice feature of this type of magazine is that it can hold a lot of cartridges in a pretty compact space.

Unfortunately for Calico, the Federal Assault Weapons ban came into effect in 1994 (and was in effect until 2004). This law stated that no firearms manufacturer could produce magazines with greater than 10 cartridge capacity. Therefore, Calico could not really sell their firearms during this period because their biggest selling point was that the magazine could hold a lot of cartridges. Only after 2004 when the law was changed, could they restart manufacturing their firearms. Calico now offers firearms that have 50 and 100 cartridge capacities.

The idea of a helical magazine was copied by other countries, most notably by Russia, China, Hungary, North Korea etc.. The Russian Bizon submachine gun is one such weapon that uses this concept.

Bizon submachine gun. Click on the image to enlarge.
Image is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license by Vitaly Kuzmin

The above image is a Russian Bizon submachine gun. The word Bizon is the Russian word for "Bison". The long cylindrical tube that you see under the barrel in the image above is the helical magazine. It comes in two versions: one is chambered for the 9x18 mm. Makarov cartridge and the other model uses the popular 9x19 mm. Parabellum cartridge. Magazine capacity is 64 cartridges for the Makarov cartridge and 53 cartridges for the Parabellum cartridge. Incidentally, two of the designers of this firearm have very famous parents as well: Viktor Kalashnikov (son of Mikhail Kalashnikov, designer of the AK-47) and Alexi Dragunov (son of Evgeny Dragunov, inventor of the SVD sniper rifle).

Compared to box magazines (which can hold about 30-40 magazines before becoming unwieldy), helical magazines can hold a lot more cartridges in a relatively compact space. However, unlike drum magazines, a helical magazine does not stick out of a firearm so much as to affect the balance and ergonomics. On the other hand, helical magazines have a lot more parts than other magazine types (as you can see by the image of the magazine sub-assembly above), so disassembling one can be complicated. Also, loading and unloading the magazine must be done one round at a time, which means it can take a while to do this.

Monday, June 23, 2014

Rotary Magazines

A few posts ago, in our study about capsule magazines, reader William Reichlinger posted an interesting comment asking whether a 1941 Johnson rifle uses a capsule magazine or not and that wikipedia mentions that it is a rotary magazine and whether it is a subclassification of a capsule magazine or not. Therefore, in today's post, we will study all about the rotary magazine.

To answer the question briefly, a rotary magazine uses a different feed mechanism than a capsule magazine. A capsule magazine has a spring and follower to push rounds from the magazine into the chamber and it is always a fixed magazine. A rotary magazine, on the other hand, can be either a fixed or detachable magazine and the feeding mechanism consists of a sprocket (or sprockets) that is rotated by a torsion spring. The cartridges fit between the teeth of the sprocket and as the sprocket rotates, it feeds the rounds to the chamber. The figure below shows the various parts and the completed assembly of a rotary magazine.

Parts of a rotary magazine. Click on the image to enlarge.

The cartridges fit between the teeth of the two sprocket wheels and are fed into the chamber of the firearm, powered by the tension of the torsion spring.

One of the early designs for a rotary magazine design is by Otto Schonauer in 1885. Otto Schonauer was a protege of the famous German firearms designer, Ferdinand Mannlicher and his rotary magazine design appeared in a turnbolt Mannlicher .43 caliber rifle design in 1887. However this rifle was not very successful and the magazine was not perfected yet. A much improved rotary magazine was featured in the Mannlicher-Schonauer M1903 rifle design, which was very successful.

Diagram of a Mannlicher rotary magazine by itself. Click on the image to enlarge
 A Mannlicher rotary magazine attached to a rifle. Click on the image to enlarge.

Meanwhile, over in the United States, Arthur Savage was also working on a rotary magazine design, which he perfected in 1893 and obtained a patent for it. This design was used in the Savage M1895 and Model 99 rifles.

Patent documentation for the Savage Model 99 rotary magazine. Click on the image to enlarge. Public domain image.

Interestingly, this rifle's rotary magazine design also includes a counter that shows the user how many cartridges are left in the magazine. It must be noted that not all Savage Model 99 rifles have this rotary magazine, as some later versions feature a box magazine instead. The Model 99 was produced by Savage for nearly 100 years (1899 - 1998) and has been chambered for many different cartridges.

Another firearm that uses a rotary magazine is the Johnson M1941 rifle, which we mentioned at the start of this post. This rifle was invented by Melvin Johnson and the magazine design is shown below from his patent application:

Click on the images to enlarge. Public domain images.

The entire Johnson patent document may be viewed online here.

Some other firearms that use this sort of magazine include the hugely popular Ruger 10/22 rifle and the Steyr SSG 69 rifle.

A rotary magazine used by a Ruger 10/22 rifle. Click on the image to enlarge. Public domain image.

The above image shows a rotary magazine used by a Ruger 10/22 rifle. This particular model holds 10 cartridges and is made of clear polycarbonate plastic and allows the user to see how many cartridges are left in the magazine. Many American readers of this blog will recognize this type of magazine because this is what comes with the standard model of the Ruger 10/22 rifle. For non-American readers, the Ruger 10/22 is one of the most popular rifle models in the US since 1964, because of its affordable price, ability to be customized, widespread availability of third party components and low cost of ammunition, and it is often the first rifle for many Americans.

Rotary magazines typically have a capacity of around 5 to 10 cartridges, which means they don't hold as many cartridges as some of the other magazine types we studied earlier. On the other hand, many rotary magazine designs fit right into the magazine's stock, without protruding out like a box magazine or a drum magazine do, which makes them much more convenient. In some rifles, the rotary magazine fits right where the center of gravity of the rifle is. Rotary magazines can also use spitzer type pointed bullets safely. In fact, the Savage Model 1895 was one of the first lever-action rifles to use spitzer bullets, as previous lever-action rifles used tubular magazines, which as we saw earlier, are not safe to use with centerfire cartridges using spitzer bullets.

Monday, June 16, 2014

Pan Magazines

In our last post, we studied the drum magazine. In today's post, we will study another type that looks very much like the drum magazine, but operates a bit differently. Today's object of study will be the pan magazine.

The pan magazine is a flat cylindrical shape, similar in shape to a drum magazine. However, if you look at the previous post, drum magazines are mounted from below the gun. A pan magazine, on the other hand, is mounted on top of the gun and uses the force of gravity to drop cartridges into the action. One more difference is that the cartridges in a pan magazine are arranged perpendicular to the axis of rotation, whereas the cartridges in a drum magazine are arranged parallel to the axis of rotation. The easiest way to understand it is via some pictures.

A pan magazine from a Lewis gun. Click on the image to enlarge.

As you can see from the above image, the cartridges are arranged like the spokes of a wheel in a pan magazine. Compare this to how the cartridges are arranged in a drum magazine, as seen in our previous post.

One of the first firearms to feature a pan magazine, was the Bira gun, which we studied many months ago.

A Bira Gun. Click on the image to enlarge.

The flat circular object that you see on top of the gun is the pan magazine. In the Bira gun, this magazine is designed to hold .577-450 Martini cartridges in two layers of 60 cartridges each, giving the magazine a capacity of 120 cartridges. As the crank (which can be seen on the side at the rear of the gun) is turned, the magazine is rotated via a ratchet mechanism. There is a stationary plate at the bottom of the pan, which has a slot in it, big enough for a cartridge to fall through into the action.

Another gun that features a pan magazine was invented in 1898 by Howard Carr, a well-known shooter (he once held a world-record for pistol shooting), and manufactured by the San Francisco Arms Company. The details of his patent may be viewed here.

Image from Howard Carr's machine gun patent claim. Public domain image. Click on the image to enlarge.

In the above drawing, note how the cartridges sit on top of each other in the magazine. This allows the magazine to hold a large number of cartridges.

Some other guns that feature pan magazines are the Lewis gun, the Bren light machine gun, the Degtyarev light machine gun and the American-180 submachine gun. 

A Lewis gun. Click on the image to enlarge. Public domain image.

A Degtyarev gun. Click on the image to enlarge. Image copyright Polish Ministry of National Defense and used with permission.

In the case of the Bira gun and the Lewis gun, the pan magazine has notches or teeth on the outside of the magazine cover, which can be driven by a ratchet and pawl mechanism. In the case of a Bren gun or an American-180, the magazine is rotated by unwinding a circular spring.

Like drum magazines, pan magazines can hold a pretty large number of cartridges. The Bira gun's capacity is 120 cartridges, the Howard Carr machine gun magazine holds 310 cartridges, the Bren magazine holds 100 cartridges, the Lewis gun holds 47 or 97 cartridges, the Degtyarev holds 47 or 60 cartridges and the American-180 can hold 165, 177, 220 or 275 cartridges, depending on the model of magazine. Since a pan magazine sits flat on top of the gun, this means the gun doesn't take up too much vertical height and this allows the soldier to lie prone on the ground without exposing himself much.

Tuesday, June 10, 2014

Drum Magazines

In our last post, we studied the capsule magazine. In today's post, we will study a type of magazine that is known for its capacity. Today's object of study will be the drum magazine.

This type of magazine is a flat cylindrical shape, similar in shape to a drum, which is why it is called a "drum magazine". These magazines can generally hold a lot of cartridges inside them. The gun that was originally associated with the drum magazine was the Thompson submachine gun, otherwise known as the "Tommy Gun", "Chicago Typewriter", "Trench Broom" etc., which was first produced in 1918.

A Thompson submachine gun with a drum magazine attached.
Click on the image to enlarge.

The above image shows a Thompson submachine gun with the drum magazine attached. Now let's look at the mechanism from the inside:
Drum magazine internals. Click on the image to enlarge.
Image licensed under the GFDL from user Hmaag at wikipedia

The above image shows both drum and box magazines, but we will only consider the drum magazine here. This drum magazine has a coil spring, which is wound up using a key. The unwinding coil spring powers a spider gear assembly, which is used to push the cartridges along a spiral path towards the opening on the top of the magazine. To load this type of magazine, the key is removed and the top cover of the magazine is lifted up to expose the interior of the magazine. Then cartridges are filled into each of the compartments, first filling the outer ring and then moving on to the inner ring. Then the magazine cover is placed back into position and the key is wound up to a certain number of clicks, depending on the capacity of the magazine.

The Thompson submachine gun is designed to use four different types of drum magazines of different capacities. The L-type drum magazine (which is the most common) holds 50 cartridges, the C-type drum magazine (which is much rarer) holds 100 cartridges, the XL-type drum magazine holds 39 cartridges and finally, the X-type drum magazine that holds only 10 cartridges (this was designed due to firearm laws enforced at that time.) As you might have possibly guessed, the names L, C, XL and X are because they are the Roman numerals corresponding to the magazine capacities.

Th spider gear type of drum magazine design is pretty commonly used in other firearms as well, most notably, the AK family of firearms (e.g. AK-47, AKM etc.)

Another common type of drum magazine is the Beta C-Mag, designed by Jim Sullivan and manufactured by the Beta Company. 

Schematic illustrations of Beta C-Magazines, filled and empty. Click on images to enlarge.
Images licensed under the Creative Commons Attribution 3.0 Unported license by Martin Miese at wikipedia.

The magazine has twin drums with a feed clip assembly in between. The feed clip assembly is interchangeable to accommodate specific firearms. There are a few spacer cartridges in the magazine (illustrated above in red, black and blue colors) and these are actually part of the magazine and do not get loaded into the firearm. Their purpose is to push the actual cartridges to the top of the feed assembly as the magazine is emptied. The top spacer cartridge (which is colored red in the images above) is tapered, so that when the firearm fires its last round, the bolt closes without picking up the spacer cartridge. To load this type of magazine, new cartridges are pushed in at the top of the feed clip and the cartridges are evenly split into the two drums. The rotors in the two drums are driven by springs, which push the cartridges out of the magazine as needed. 

An 82nd Airborne Division paratrooper firing his M4 equipped with a Beta C-Mag. Click on the image to enlarge. Public domain image.

A Beta C-Mag can hold up to 100 cartridges. Unlike the earlier drum magazine we studied, this one is a lot more compact because of the double drum design and also distributes the weight better. This type of magazine is available for several firearm models, including the M16 family, M14 rifle, FN FAL, Steyr AUG etc.

In general, drum magazines have much higher capacities compared to box magazines. However, they have been prone to jamming problems and they also tend to increase the weight and alter the balance of the firearm.

Tuesday, June 3, 2014

Capsule Magazines

In our last post, we studied a type of magazine that is widely used in modern firearms, the box magazine. In today's post, we will study a type of magazine that came out around the same time as the box magazine, but is not seen in much use today. We are talking about the capsule magazine.

There is really only one somewhat famous model of rifle that ever used the capsule magazine. However, this rifle was pretty influential and was adopted as the military rifle of three countries: Denmark, Norway and the United States of America. This rifle was the Krag-Jorgensen rifle.

The Krag-Jorgensen rifle was designed in 1886 by a Norwegian officer Ole Herman Johannes Krag and a Norwegian master gunsmith, Erik Jorgensen. Captain Krag had already had some experience in designing firearms at this point, as he had designed the Krag-Petersson rifle (with Swedish engineer Axel Petersson) in 1876, which was already used by the Norwegian navy. The earlier Krag-Petersson rifle, as well as the Jarmann rifle (used by Norway and Sweden) both used tubular magazines and Captain Krag was somewhat dissatisfied with the reliability of the tubular magazine. Therefore, he enlisted the help of a master gunsmith called Erik Jorgensen to design a new type of magazine for a new rifle. The result was the capsule magazine.

The interesting thing about this magazine is that unlike the tubular magazine, which is a straight tube that is generally positioned under the barrel, this magazine wraps around the action of the rifle. The cartridges in a capsule magazine are loaded parallel to each other, similar to a box magazine and unlike a tubular magazine. The following pictures will make it clear how the magazine works.

Side view and sectional view of the Krag Jorgensen rifle. Click on the images to enlarge. 
Images are in the public domain.

In the above  images, we see two views of the rifle, a sideways view and a sectional view of the magazine. The second picture makes it clear how the cartridges wrap underneath the action and are loaded into the chamber.

There is an opening on the right side of the rifle, which is covered by a hinged door. Cartridges are pushed one at a time, through this opening and the spring and follower push the cartridges around and up into the action. A nice feature of this type of magazine is that it is easy to refill it, and unlike the internal box magazines we saw in the previous post, the user does not need to lock the bolt back to do this.

The original Krag-Jorgensen rifles were designed to hold 10 cartridges in the magazine. In 1886, the Danes held a trial for a new military rifle and an early Krag-Jorgensen rifle was submitted as an entry to the competition. The feedback of the Danish military revealed the need to lighten the rifle and therefore, the designers reduced the magazine capacity to 5 cartridges.

One more interesting feature of this rifle is that it has a magazine cut-off lever, which can be seen in the second picture. The reason for this lever is because of the military thinking of the day. Generals believed that if they gave soldiers the capacity to rapidly fire at long ranges, they would spend less time aiming carefully and would waste ammunition. However, if there was a need to charge at the enemy, or to defend against an enemy's charge, then a rapidly firing weapon was needed. This is why the cut-off lever was included. When the lever is flipped up, it blocks the cartridges in the magazine from being picked up by the bolt action. This means, the soldier has to open the bolt manually, load a single cartridge in the chamber, push the bolt back and use it as a single-shot weapon. When the cut-off lever is flipped down, it allows the bolt to pick up a new cartridge from the magazine upon closing the bolt. The military thinking was that soldiers could load the magazine up fully, but flip the cut-off lever up and use the rifle in single shot mode when firing at enemies at long distance, thereby conserving the ammunition stored in the magazine. If they needed to charge an enemy or defend against an enemy charge, they could flip the cut-off lever down and use the ammunition stored in the magazine for extra firepower.

A Krag-Jorgensen Model 1892 rifle. Click on the image to enlarge. Public domain image.

The Krag-Jorgensen was selected by the US military in 1892 and served until 1903, when it was replaced by the Springfield M1903, which could handle more powerful ammunition and could be loaded faster via stripper clips. So far as your humble editor has heard, the Krag-Jorgensen was the sole user of the capsule magazine and no other firearm has used this unique type of magazine.

In the next few posts, we will study other types of magazines.

Sunday, June 1, 2014

Box Magazines

In our last post, we studied tubular magazines. In today's post, we will study a type of magazine that is commonly seen in modern firearms, the box magazine.

In the latter part of the 1800s, bullets became more and more pointed (spitzer type bullets) because of better efficiency and accuracy over longer ranges. However, storing cartridges using pointed bullets in a tubular magazine wasn't a very good idea, for reasons we already studied in the previous post. The box magazine was invented to allow safe storage of cartridges of this type. Instead of storing the cartridges nose to tail (like a tubular magazine does), a box magazine stores the cartridges parallel to each other. A spring at the closed end of the magazine pushes the cartridges outwards.

There are two types of box magazine: the internal (or fixed) magazine and the detachable magazine.

Internal magazines are generally seen on bolt-action rifles and usually hold about 5 to 10 cartridges. They can be filled by hand, or more quickly by using clips, such as stripper clips or en-bloc clips to shove in multiple cartridges at a time. An internal magazine is not easily removable from the firearm.

A Lee-Enfield No. 1 Mark III rifle. Notice the internal magazine in front of the trigger. Click on the image to enlarge. Public domain image.

The above image shows a Lee-Enfield Mark III rifle. Note the internal magazine in front of the trigger. This rifle is loaded by opening the bolt on top of the rifle and pushing cartridges into the magazine. The magazine holds up to 10 cartridges. The cartridges can be fed in one at a time by hand, or by using a stripper clip containing 5 cartridges and pushing them into the magazine simultaneously. The video below shows how this is done.

Detachable magazines are designed to be attached and removed from the firearm and can be loaded separately. This allows the user to carry multiple magazines that are pre-loaded with cartridges and quickly switch between them as needed. Detachable magazines are generally loaded at the bottom of the firearm (e.g. most modern pistols, submachine guns, semi and fully automatic rifles etc.), but there are a few famous exceptions. For instance, the Sten and Sterling submachine guns have their magazines attaching to the side of the firearm, and the Bren gun and Madsen machine gun have magazines that attach on the top. Detachable magazines may be straight or curved, depending on how many cartridges they hold and the type of cartridge.

Two detachable box magazines. Left is a 20 round magazine made by Colt, right is a 30 round "High Reliablility" magazine made by Heckler & Koch.
Click on the image to enlarge.
Image licensed under GNU Free Documentation License v 1.2 or later, by user Raygun on wikipedia.

The video below shows how to interchange detachable magazines on a pistol.

The invention of the box magazine is generally credited to two Scottish born Canadian brothers, James Paris Lee and John Lee. In 1878, they invented a rifle, whose box magazine design was used by the Lee-Metford and later, the Lee-Enfield rifles.

The original Lee Rifle prototype. Click on the image to enlarge. Public domain image.

The above image shows the first Lee rifle prototype. The box magazine is visible under the stock, just ahead of the trigger guard. The magazine that this rifle uses is an internal magazine.

Box magazines store their cartridges in columns, either one above the other (single column a.k.a single stack magazine) or in a zigzag manner (double column a.k.a double stack magazine or even quadruple column a.k.a casket magazine). The images below show the different styles of magazines.

A single column (single stack) magazine. Click on the image to enlarge.
Image licensed under the Creative Commons Attribution 3.0 Unported License from Martin Meise at Wikipedia.

A double column (double stack) magazine. Click on the image to enlarge.
Image licensed under the Creative Commons Attribution 3.0 Unported License from Martin Meise at Wikipedia.
A quadruple stack (casket) magazine for a Spectre M4 submachine gun. Click on the image to enlarge.
Image licensed under the Creative Commons Attribution-Share Alike 2.0 License from Evers at Wikipedia

In the above illustrations, notice that each magazine has a spring and a follower piece at the bottom of each magazine. The spring and follower keep the cartridges pushed towards the top of the magazine, where they may be picked up by the firearm's action.

Box magazines can be made of either metal or plastic. In some firearms, the plastic magazines are made of a transparent material, which allows the user to easily see how many cartridges are left in the magazine.

Box magazines are loaded by hand, or more quickly by devices such as stripper clips, en-bloc clips, speed loaders etc. We already studied stripper clips and en-bloc clips two posts ago. In the images below, we see two other speed loading devices designed for M-16 magazines:

A bench loader and a strip loader for M16 magazines. Click on the images to enlarge.
Images are in the public domain.

People who use pistols may be familiar with a device called a "thumb saver", which is sometimes used to load magazines. Basically, a box magazine is usually pretty easy to load by hand, except for when the magazine is almost full. The last couple of cartridges are usually very hard to push in manually and thumb savers reduce the effort required to do this (and prevent sore fingers and thumbs!).

Box magazines have a number of advantages over tubular magazines:

  1. They can safely hold cartridges that have spitzer-type (pointed) bullets, which tubular magazines cannot do.
  2. They can hold a fairly large number of cartridges, compared to tubular magazines. 30 round magazines are very common for rifles, for instance.
  3. If they are made of plastic, they can be made transparent (this isn't always done, but is transparent on some models) so that the user can see how many cartridges are left in the magazine. Since tubular magazines are generally enclosed by the stock of the firearm, the user cannot see how many cartridges are left in a tubular magazine.
  4. The user can preload a bunch of magazines in advance and can quickly switch between them (at least, for detachable box magazines).
  5. It is easier and faster to load or unload a box magazine than a tubular magazine.

Because of these numerous advantages, box magazines are the most common type of magazine used by modern pistols, submachine guns and rifles today.