
45ACP, with the abbreviation standing for Automatic Colt Pistol. On this side of the pond, rather than specify the bullet diameter and the length of the case, we typically just label a cartridge by caliber and who invented it.įor example, instead of 11.43x23mm, Americans would call the same round a. For instance, an 11.43x23mm round has an 11.43mm (.45-caliber) bullet diameter on a case that is 23mm long. Metric cartridges will include the case lengthĪdded to this in metric cartridges is typically the length of the cartridge’s case. This rule largely converts back and forth with such general examples as 5.56mm/.223-caliber, 6.35mm/.25-caliber, 7.62mm/.30-caliber, 11.43mm/.45-caliber, and so forth. or Great Britain, that size will typically be listed in terms of 1/100th (hundredth of an inch), a portion deemed a “caliber.”įor instance, a firearm with a quarter-inch bore will be “.25-caliber.” For pistols, revolvers, and rifles made in areas that have long been on the metric system, the bore will be in millimeters. On pistols, revolvers, and rifles made in the U.S.

Modern firearms make it (relatively) easyĪll modern firearms will list the bullet chamber size either on the frame/receiver or the barrel. One thing that is abundantly clear to all gun owners is that you should only try to load ammunition into a firearm that it is designed for.
