You can find ballistic reports and technical information galore on firearms and ammunition. But when it comes to explaining the way ammunition names are designated the waters become rather muddy.
The caliber of ammunition is generally the diameter of a bullet. But the size of the caliber is not necessarily the exact diameter in many cases. It also wouldn’t be inaccurate to say caliber is an approximation of a bullets diameter, for a lot of ammo. Let’s look at some of the most popular and how they actually measure up.
The .44 Remington Magnum shoots a bullet that can vary from .429” to .431” diameter. While some gun owners may be surprised at this fact they already know it to be an extremely effective weapon, though not the best choice for self-defense due to the fact that this powerful gun is quite capable of passing through an assailant and into bystanders.
A .38 Special bullet is .357 in. diameter and is designed for revolvers. Available in standard and +p variants, which is plus power. Never attempt to fire +p ammo in revolvers from pre-modern metallurgy days. Older guns simply will not handle the extra power and pose a safety hazard to life and limb. Use only Standard rounds in older pistols. Don’t trust the clerk, check the box yourself. Some modern firearms constructed of light weight alloys also won’t be able to handle the extra punch of +p ammo. Read your owner’s manual, or call the manufacturer to ensure you can safely use +p ammunition before you try.
The .45 ACP combines a bullet diameter of .452” with initials for its original firearm, the Model 1911 Automatic Colt Pistol, or ACP.
The 30-30 Winchester refers to a bullet diameter of .308” and a theoretical 30 grains of black powder. Sources say it’s theoretical because the 30-30 was never loaded commercially with black powder. Winchester simply continued its previous method of cartridge-naming as a convenience to shooters already familiar with this method, and the smokeless load was approximately equal to 30 grains of black powder, hence 30-30.
The 30-06 bullet diameter is .308” and the 1906 stands for the year it was adopted by the US military.
A 9mm bullet is 9.01 mm in diameter (0.355”). The 9 × 19 mm Parabellum cartridge was designed by George Luger and introduced in 1902 by the German weapons manufacturer Deutsche Waffen-und Munitionsfabriken or (DWM). The 9mm Parabellum derives from the Latin Si vis pacem, para bellum. Translated it means, “If you seek peace, prepare for war”, and was the motto of DWM.
Ammunition can become even more complicated when you compare ammo for handguns versus ammo for rifles of the same caliber. Let’s use the common .22 as an example.
.22 Long Rifle or .22LR
This ammo can be fired from both handguns and rifles even though it has “Rifle” in its name.
This bullet has the same diameter as the .22LR but a shorter case. It doesn’t have as much power as the .22LR because it doesn’t have as much powder in its shorter case.
.22 Winchester Magnum Rimfire or .22WMR or .22 Magnum
This bullet is slightly larger in diameter than the .22 LR or .22 Short. The case is slightly longer because it packs a little more powder making it slightly more powerful. It can be used in both handguns and rifles. Do not use .22 LR ammo in a revolver chambered for .22 Magnum. They are different calibers and exchanging them can be dangerous resulting in severe injury or death. Always refer to your owner’s manual or the manufacturer to ensure the proper ammunition is used for any firearm.
It is a fairly accurate summation to say that naming methods has varied over the years. What is important is that you use the correct ammunition in a gun.
Check the box, read it, it is your responsibility to ensure you have the correct ammo. When in doubt, read your owner’s manual, or call the manufacturer, and never substitute ammunition. Just because the number is the same doesn’t mean it is the same, or that it will be safe to use.
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