A rifle’s caliber is the diameter of its barrel, measured in inches or millimeters. Rifles are sometimes referred to by caliber and sometimes by the specific cartridge(s) that they can take. This article provides an overview of rifle calibers and how rifle calibers can affect your shooting.
Introduction to Rifle Calibers
Although obviously, a cartridge has to be smaller than the inside of the barrel to pass through it, cartridges often have a name that combines their manufacturer and the caliber weapon that takes it. Firearms and cartridges to fit them can be made in conjunction, or firearms can be made to fit available caliber bullets.
Often a manufacturer will release a new size cartridge and a firearm with a new caliber to match. But this doesn’t always go as expected. For example, in 1990, Smith & Wesson and Winchester introduced the .40 S&W cartridge, but Glock was able to beat them to the punch by developing and releasing a pistol to fire it (the Glock 22) and a compact version of the same pistol (the Glock 23) before the Smith & Wesson Model 4006 pistol came to market, a little later in the year.
Rifle calibers can be designated in inches or millimeters.
Measurements in inches usually show a decimal to the hundredths or thousandths place (.22 or .338), but sometimes the decimal point is omitted (22).
Measurements in millimeters may have a whole number (9 mm) or include tenths (6.5 mm). Some metric measurements follow the diameter of the bullet (width) with the length, with an x in between (7.62 x 51). When the length is given, mm may not be included.
In metric measurements, the decimal is never omitted. Because cartridges are measured in a variety of ways, equivalently named cartridges as far as caliber are not always interchangeable.
Rimfire rifles are made in a limited number of calibers: .17, .22 and 5mm. Centerfire cartridges are a different story. Cartridges for centerfire rifles can range from .17 caliber to .950. Given the small size of the diameter of rifles barrels, it is not surprising that there are cartridges with incremental differences, for example, .220, .221, .222, .223, .224, and .225 are all available calibers. In fact, even though you may hear of a few calibers more than others, there are actually many, many choices.
Rimfire and Centerfire Rifle Calibers
Various calibers cartridges may be sorted by purpose on account of the range, recoil, size bullet it can handle, trajectory, and how it can be fired (singl, from a magazine, from an ammunition belt, etc.). However, this does not eliminate controversy and arguments about which cartridge (and which caliber cartridge) is best for various purposes.
Some of the most popular caliber cartridges are the .22LR (Long Rifle), which is used for small game, target shooting, and plinking;
.308 Winchester (aka 7.62×51 mm NATO), which is used by military snipers, big game hunting, and law enforcement sharpshooting;
5.56x45mm NATO adapted from the .223 Remington and used in assault rifles.
As you can see there are many types of Rifle calibers. In fact, so many rifle calibers that you can easily become confused! The best thing to do is do your research and find out which rifle caliber is best for you then find the perfect rifle for you.