Sunday, February 24, 2013

How did they name cartridges - II

When we left off in our last post, we saw that cartridges like .45-70 and .50-90 were named based on their caliber and the amount of black powder in it (e.g. .45-70 has a bullet of .45 inches in diameter and 70 grains of black powder). We also saw that if two different bullet weights were available for the same cartridge, then a 3 number scheme was used (e.g. .45-70-405 and .45-70-500, where the 405 or 500 indicates the weight of the bullet in grains). We will continue our discussion in this post.

With the invention of newer smokeless powders, cartridges still retained the same two digit naming scheme as before: e.g. the famous .30-30 Winchester rifle, .32-20 Winchester or the .30-40 Krag, which replaced the .45-70 in US military service. As before, the first number indicates the caliber (e.g. 0.30 inches diameter) and the second number indicates the amount of smokeless powder in grains.

After some years, people began to drop the amount of grains and use the year that the cartridge was introduced instead. For instance, the Springfield .30-06 cartridge. This cartridge's diameter is 0.30 inches and it was introduced in 1906 (from which we get 06) and therefore it was named as .30-06. The .30-06 actually replaced the .30-03, which was, predictably, adopted in 1903.

Some years after that, people began to drop the second number altogether and simply name the cartridge after the caliber and the company that introduced it  (e.g.) .44 Colt introduced by Colt firearms, .32 S&W invented by Smith and Wesson etc. Sometimes they were named after a specific product (e.g.) .45 ACP where ACP stands for Automatic Colt Pistol. Sometimes they were named after specific attributes (e.g.) .38 Special, .44 Magnum, .577 Express etc., where the words Special, Magnum or Express indicate that these cartridges have extra power.

By the 1950s, people also started to name the first number by the groove diameter of the rifle, rather than the bore diameter of the bullet (at least in America). For instance, .308 Winchester, where the bore diameter is 0.300 inches, but the groove diameter is 0.308 inches.

Over in Europe (except for the UK), people generally use the metric system and name cartridges with two sets of numbers separated by an "x". e.g. 7.62x51, 5.56x45 etc. The first number is the bore diameter of the bullet in millimeters (e.g. 7.62 mm., 5.56 mm. etc.) and the second number is the length of the case in millimeters (e.g. 51 mm., 45 mm. etc.). Note that the first number is the bore diameter, not the groove diameter. Therefore, what we call the .308 Winchester in America actually has a bore diameter of 0.300 inches and a groove diameter of .308 inches and the Europeans take the 0.300 inch measurement and convert that into millimeters (7.62 mm.) and use that in their cartridge nomenclature. This system is generally used in the rest of the world as well (Asia, Africa, South America, Oceania etc.)

The British tend to name their cartridges in American fashion, e.g. .244 H&H Magnum (where H&H stands for Holland and Holland, a famous British firearms firm), .455 Webley (invented by Webley, another British firearms manufacturer) .700 Nitro Express etc. The numbers indicate the diameter of the bullet rather than the groove diameter though.

These are generally the naming schemes in vogue these days, but there are exceptions to the rule. American manufacturers in particular, tend to add names that sound good to consumer ears: e.g. .22 Hornet, .221 Fireball, .224 Rocket etc. Also, there are cartridges such as the .280 Remington (which actually has a bore diameter of 0.277 inches and groove diameter of 0.284 inches) and the .260 Remington (which actually has a bore diameter of 0.256 inches and groove diameter of 0.264 inches). Remington's marketing people decided that customers like numbers that end in zero better, so they named then .280 and .260 instead.

As you can see, these are several ways how cartridges have been named throughout history.

Wednesday, February 20, 2013

How did they name cartridges - I

In the world of firearms history, we often see famous cartridge names like .30-30 Winchester, .45 ACP, .30-06 Springfield etc. So how exactly do cartridges get named and is there some meaning behind their naming convention. We will study those in this post.

Bear in mind that cartridges are not always referred by the same name throughout history. For example, when Smith & Wesson produced their first revolver model, they made it fire a .22 cartridge, which was then referred to as a ".22" or a ".22 caliber" in 1857, since there were no other cartridges with the same caliber bullet. This cartridge contained 4 grains of black powder in it and a bullet weighing 29 grains (or 2 grams in the metric system) and measuring .222 inches in diameter. In 1871, Smith & Wesson produced another cartridge in .22 caliber diameter. This cartridge used the same 29 grain bullet as its predecessor, but the case was a bit longer than the older one and contained more black powder (5 grains), in order to produce extra power. Therefore, they began to refer to the old .22 cartridge as ".22 Short" and the new one as ".22 Long". Both these cartridges were used for revolvers. Soon afterwards, Remington, Stevens, Winchester etc. started producing the ".22 Extra Long" for rifles and revolvers. This cartridge used a 40 grain (3 gm.) bullet and a longer case that contained 6 grains of black powder in it. Then, the Stevens Arms and Tool Company combined the case of the .22 Long with the 40 grain bullet of the .22 Extra Long to produce the ".22 Long Rifle" (a.k.a. ".22 LR" cartridge).

Public domain image of different .22 caliber cartridges.

The .22 LR became very successful and still remains the most popular cartridge in the present day. Therefore when someone talks about ".22 caliber" in today's world, they are almost certainly referring to the .22 LR cartridge. However, back between 1857 and 1871, when someone said ".22 caliber" they would have been referring to what we now call ".22 short". So you can see how common cartridge designations have changed over the years.

For some early cartridges, they were named with two sets of numbers. For instance, right after the US Civil War, the US government issued the ".50-70 Government" cartridge for use with the Springfield Model 1866 rifle. This was later replaced by the ".45-70 Government" cartridge in 1873. So what do the numbers .50-70 and .45-70 mean? For a ".50-70", it means that the cartridge has a .50 caliber bullet and 70 grains of black powder. Similarly, a ".45-70" has a .45 caliber bullet and 70 grains of black powder. This naming scheme was also used for other cartridges such as the ".50-90 Sharps", ".50-100 Sharps", ".50-110 Winchester" etc.

In some situations, these cartridges were also referred to with three sets of numbers, such as ".50-70-450" and ".45-70-405" where the third number indicated the weight of the bullet in grains. This was done as cartridges of the same size, but with different bullet weights, became common. For instance,  the .45-70 cartridge case was used for two different bullet weights and to tell them apart, the two cartridges were called .45-70-405 and .45-70-500, when the 500-grain-bullet variant was invented in 1884.

In the next section, we will look more into the conventions used to name cartridges.

Saturday, February 16, 2013

What is +P and +P+ Ammunition?

In the world of firearms, some of you readers may have heard about the terms +P and +P+ (pronounced as "Plus-P" and "Plus-P-Plus"). So what is this all about anyway?

In the US, several firearms and ammunition manufacturers jointly formed a standards body called SAAMI (Sporting Arms and Ammunition Manufacturers' Institute) at the behest of the US government in 1926. This organization was charged with setting standards for the firearms industry and contributes its specifications and documentation to the American National Standards Institute (ANSI). All major manufacturers of firearms and ammunition in America are members of the SAAMI association, as are many of the smaller manufacturers. While the SAAMI association requires its members to follow the standards and guidelines that it sets, the US government does NOT enforce the SAAMI standards by law (unlike the European CIP standards, which are a compulsory standard enforced by law in several European countries). It is also not required for a manufacturer to be a member of the SAAMI association either (and some smaller ammunition manufacturers are not and therefore not required to follow SAAMI standards). These two facts are important as we will soon see.

One of the SAAMI association's jobs is to define the maximum pressure allowed to be generated by various cartridge calibers. Some of those standards were defined a long time ago (e.g. 9 mm. Luger, .45 Colt, .38 Special etc.) and it became clear that many modern firearms could easily withstand higher pressures than what the SAAMI standards said, because of improvements in metallurgy techniques. Some law enforcement departments began to clamor for more powerful cartridges to increase the effectiveness of their handguns and some manufacturers began to manufacture +P cartridges, with the +P to indicate that the cartridge was loaded to generate higher pressures than the SAAMI standard. The +P sign would be stamped on the cartridge box and on the base of the cartridge as well.

A 9mm. Luger +P cartridge on the left and a regular 9 mm. Luger cartridge on the right. Note the letters "+P" stamped on the left.

Soon, SAAMI got into the act and established an official +P standard for a few common cartridge types. Typically +P ammunition generates about 10% more pressure than the non +P type, though this is not true for all cartridge types. For instance, plain 9 mm. Luger ammunition is supposed to generate a maximum pressure of 35000 PSI (Pounds per Square Inch), but 9 mm. +P Luger ammunition can generate a maximum pressure of 38500 PSI per the SAAMI standards. The idea behind the +P standards is that older firearms can use the regular ammunition and newer firearms which are built to higher standards may be able to use both regular and +P ammunition safely. While there are SAAMI standards in place for +P ammunition for some calibers (SAAMI only specified them for 5 cartridges types), there are manufacturers that make "+P ammunition" for other calibers as well. Since the SAAMI standards are not enforced by law, manufacturers can mark any ammunition as +P even if SAAMI doesn't have a standard for it. This is even more so for manufacturers who are not members of the SAAMI association.

Soon, some ammunition manufacturers (such as Federal, Winchester and Remington) started making even more powerful ammunition than +P and called these as "+P+". These were meant to be sold to law enforcement officials only, but this is not always enforced. Some think that this was merely a marketing tactic to make it appear as though non-law-enforcement buyers were getting something really special and forbidden.

+P+ ammunition standards are not defined by SAAMI, but general industry agreement is that it should be about 10-15% more powerful than +P ammunition. For example, 9 mm. +P+ Luger ammunition generates a maximum pressure of about 42,000 PSI.

Using overpressured ammunition increases the wear and tear of firearms. While more modern firearms can handle higher pressures, older firearms cannot handle +P and +P+ ammunition that well and may have safety issues. That is why it is advisable to check the user manual to see if +P and +P+ ammunition can be used with a particular handgun model or not.

Wednesday, February 6, 2013

Why does a M16 have Tall Sights?

When we look at an M16 rifle (or its semi-automatic only civilian cousin, the AR-15), there is something noticeable about their sights:

A M16A2 and two M16A4s. Click on images to enlarge. Public domain images.

In all these examples, note that the sights are a good 2.5 inches from the top of the barrel. Why is this the case with the M16 family? We will study the reason in this post.

The first thing to notice in the M16 family of firearms is that the stock is in line with the center of the barrel. In most other rifles, the stock is a little below the line of the barrel and they have small sights mounted on top:

Click on images to enlarge. Public domain images.

The reason why the stock is below the barrel is for ergonomics. When the user rests his/her cheek on the comb of the stock. the user's eye is aligned just above the top of the barrel and therefore the sights can be placed right above the top of the barrel for such firearms.

However, for such stocks, when a bullet is fired, the recoil pushes back in the line of the barrel and the resistance offered by the user's shoulder is below the line of the barrel and this creates a rotational torque. We studied this effect when reading up on muzzle brakes and compensators earlier:

Here, A is the force acting because of the recoil and B is the force resisting the movement from the user's hand and shoulder on the grip and stock. Since A is higher than B, this causes the rotational torque C, which causes the front of the barrel to rise when shooting. This can cause a loss in accuracy, especially when firing rapidly.

In the M16 family of rifles, the rotational torque is minimized by placing the stock higher, so that forces A and B are around the same line with each other. This is called a "straight line layout" and is done in order to make the rifle easier to control, especially when firing in burst fire or automatic fire modes. One more nice feature of the straight line layout is that it allows the operating rod and buffer to run directly back into the stock and thus reduces the overall length of the rifle. However, with a straight line layout, the user cannot comfortably aim the rifle if the sights are just above the line of the barrel. Hence, the solution was to make the sights taller on the M16 family, so that the user can place their cheek on  the stock and still look through the sights comfortably.

By the way, the M16 isn't the only rifle that does this. The German FG42 and MG42 and the US M60 are three earlier examples that have tall sights as well:

FG42 and M60 machine guns. Click on images to enlarge. Public domain images.

In the above images, note that they all have a straight line layout. The FG42 was one of the first firearms to have this feature and came out during World War II. The straight line layout was later adopted by others, such as the M16 family, the Russian Dragunov rifle, the German Heckler and Koch HK36 and XM8, the Swiss SIG SG 510 etc.

A Swiss SIG SG 510. Click on image to enlarge. 
Licensed by user Rama under the Creative Commons Attribution-Share Alike 2.0 France license from

With taller sights, the user can rest his/her cheek on the comb of the stock as usual and still aim comfortably through the sights. This is why all rifles with straight line layouts have taller sights.