In guns, particularly firearms, caliber is the specified nominal internal diameter of the gun barrel bore – regardless of how or where the bore is measured and whether the finished bore matches that specification. It is measured in inches or in millimeters. In the United States it is expressed in hundredths of an inch; in the United Kingdom in thousandths; and elsewhere in millimeters. For example, a US "45 caliber" firearm has a barrel diameter of roughly 0.45 inches (11 mm). Barrel diameters can also be expressed using metric dimensions. For example, a "9 mm pistol" has a barrel diameter of about 9 millimeters. Since metric and US customary units do not convert evenly at this scale, metric conversions of caliber measured in decimal inches are typically approximations of the precise specifications in non-metric units, and vice versa.
Rimfire ammunition is a type of firearm metallic cartridge whose primer is located within a hollow circumferential rim protruding from the base of its casing. When fired, the gun's firing pin will strike and crush the rim against the edge of the barrel breech, sparking the primer compound within the rim, and in turn ignite the propellant within the case. Invented in 1845, by Louis-Nicolas Flobert, the first rimfire metallic cartridge was the .22 BB Cap cartridge, which consisted of a percussion cap with a bullet attached to the top. While many other different cartridge priming methods have been tried since the mid-19th century onwards, such as pinfire, only small caliber rimfire and centerfire cartridges have survived to the present day with regular usage. The .22 Long Rifle rimfire cartridge, introduced in 1887, is by far the most common ammunition in the world today in terms of units sold.
The .338 Lapua Magnum is a rimless, bottlenecked, centerfire rifle cartridge. It was developed during the 1980s as a high-powered, long-range cartridge for military snipers. Due to its use in the War in Afghanistan and the Iraq War, the cartridge has become widely available.
The .22 Long Rifle or simply .22 LR or 22 is a long-established variety of .22 caliber rimfire ammunition originating from the United States. It is used in a wide range of rifles, pistols, revolvers, and submachine guns.
The .44 Remington Magnum, also known as .44 Magnum or 10.9x33mmR, is a rimmed, large-bore cartridge originally designed for revolvers and quickly adopted for carbines and rifles. Despite the ".44" designation, guns chambered for the .44 Magnum round, its parent case, the .44 Special, and its parent case, the .44 Russian all use 0.429 in (10.9 mm) diameter bullets. The .44 Magnum is based on the .44 Special case but lengthened and loaded to higher pressures for greater velocity and energy.
.22 Short is a variety of .22 caliber (5.6 mm) rimfire ammunition. Developed in 1857 for the first Smith & Wesson revolver, the .22 rimfire was the first American metallic cartridge. The original loading was a 29 or 30 gr bullet and 4 gr of black powder. The original .22 rimfire cartridge was renamed .22 Short with the introduction of the .22 Long in 1871.
The .22 Hornet or 5.6×36mmR Hornet is a varminting, small-game hunting, survival and competition centerfire rifle cartridge commercially introduced in 1930. It is considerably more powerful than the rimfire .22 WMR and the .17 HMR, achieving higher velocity with a bullet twice the weight of the .17 HMR bullet. The Hornet also differs significantly from these in that being a centerfire cartridge makes it reloadable, and thus more versatile. It was the smallest commercially available .22 caliber centerfire cartridge until the introduction of the FN 5.7×28mm.
The .22 Winchester Magnum Rimfire, also called .22 WMR, .22 Magnum, .22 WMRF, .22 MRF, or .22 Mag, is a rimfire cartridge. Originally loaded with a bullet weight of 40 grains (2.6 g) delivering velocities in the 2,000 feet per second (610 m/s) range from a rifle barrel, .22 WMR is now loaded with bullet weights ranging from 50 grains (3.2 g) at 1,530 feet per second (470 m/s) to 30 grains (1.9 g) at 2,200 feet per second (670 m/s).
A wildcat cartridge, often shortened to wildcat, is a custom cartridge for which ammunition and/or firearms are not mass-produced. These cartridges are often created in order to optimize a certain performance characteristic of an existing commercial cartridge, or may merely be intended as novelty items.
The .458 Winchester Magnum is a belted, straight-taper cased, Big Five game rifle cartridge. It was introduced commercially in 1956 by Winchester and first chambered in the Winchester Model 70 African rifle. It was designed to compete against the .450 Nitro Express and the .470 Nitro Express cartridges used in big bore British double rifles. The .458 Winchester Magnum remains one of the most popular large game cartridges, and most major ammunition manufacturers offer a selection of .458 ammunition.
The .30-30 Winchester cartridge was first marketed for the Winchester Model 1894 lever-action rifle in 1895. The .30-30, as it is most commonly known, along with the .25-35 Winchester, was offered that year as the United States' first small-bore sporting rifle cartridges designed for smokeless powder. Since its introduction, it has been surpassed by many cartridges in the long-range shooting attributes of speed, energy, and trajectory, yet remains in widespread use because of its practical effectiveness in forested hunting situations.
The .300 Winchester Magnum is a belted, bottlenecked Magnum rifle cartridge that was introduced by the Winchester Repeating Arms Company in 1963. The .300 Winchester Magnum is a magnum cartridge designed to fit in a standard rifle action. It is based on the .375 H&H Magnum, which has been blown out, shortened, and necked down to accept a .30 caliber (7.62 mm) bullet.
The .22-250 Remington is a very high-velocity, short action, .22 caliber rifle cartridge primarily used for varmint hunting and small game hunting. It is capable of reaching over 4,000 feet per second. It does find occasional use by women and young children for deer hunting because of its low recoil. Some jurisdictions prohibit the use of cartridges smaller than 6 mm for deer hunting. This cartridge is also sometimes known as the .22 Varminter or the .22 Wotkyns Original Swift. Along with the .220 Swift, the .22-250 was one of the high-velocity .22 caliber cartridges that developed a reputation for remote wounding effects known as hydrostatic shock in the late 1930s and early 1940s.
The .220 Swift (5.56×56mmSR) is a semi-rimmed rifle cartridge developed by Winchester and introduced in 1935 for small game and varmint hunting. It was the first factory-loaded rifle cartridge with a muzzle velocity of over 1,200 m/s (4,000 ft/s).
The 7mm Remington Magnum rifle cartridge was introduced as a commercially available round in 1962, along with the new Remington Model 700 bolt-action rifle. It is a member of the belted magnum family that is directly derived from the venerable .375 H&H Magnum. The original purpose of the belted magnum concept taken from the .300 H&H Magnum and .375 H&H Magnum, was to provide precise headspace control, since the sloping shoulders, while easing cartridge extraction, were unsuitable for this purpose. Improved cartridge extraction reliability is desirable while hunting dangerous game, in particular when a fast follow-up shot is required. The 7mm Remington Magnum is based on the commercial .264 Winchester Magnum, .338 Winchester Magnum, and .458 Winchester Magnum, which were based on the same belted .300 H&H Magnum and .375 H&H Magnum cases, trimmed to nearly the same length as the .270 Weatherby Magnum.
The 8mm Remington Magnum belted rifle cartridge was introduced by Remington Arms Company in 1978 as a new chambering for the model 700 BDL rifle. The 8mm Remington Magnum's parent case is the .375 H&H Magnum. It is a very long and powerful cartridge that cannot be used in standard length actions, such as those that accommodate the .30-06 Springfield.
The 8×68mm S rebated rim bottlenecked centerfire rifle cartridge was developed in the 1930s by August Schüler of the August Schüler Waffenfabrik, Suhl, Germany as a magnum hunting cartridge that would just fit and function in standard-sized Mauser 98 bolt-action rifles. The bore has the same lands and grooves diameters as the German 7.92×57mm Mauser service cartridge. This is one of the early examples where a completely new rifle cartridge was developed by a gunsmith to fit a specific popular and widespread type of rifle.
The 9.3×64mm Brenneke is a rimless bottlenecked centerfire rifle cartridge designed in 1927 by German gunmaker Wilhelm Brenneke. It is suitable for hunting medium to large game animals in Africa, Asia, Europe, and North America.
The .257 Roberts, also known as .257 Bob, is a medium-powered .25 caliber rifle cartridge. It has been described as the best compromise between the low recoil and flat trajectory of smaller calibers such as the 5 mm and 6 mm, and has more energy, but is harder recoiling, similar to larger hunting calibers, such as the 7 mm and 7.62 mm.
The .270 Weatherby Magnum was the first belted magnum based on the .300 H&H Magnum to be developed by Roy Weatherby in 1943. The cartridge is short enough to function in standard-length long actions with a brass length of 2.549" or 64.74mm and an overall length of about 3.295".
