.45 caliber ammunition

.45 caliber ammunition comprises bullets (approximately 0.45 inch in diameter), first standardized by Colt's Patent Firearms Manufacturing Company in 1872.

That original .45 Colt round was developed along with the Colt Single Action Army revolver for the U.S. Army.

The .45-70 cartridge followed the next year, developed at the Army's Springfield Armory for the breech-loading Springfield Model 1873 rifle.

The .45 ACP is a cartridge designed by John Browning in 1904, for use in the prototype Colt semi-automatic .45 pistol he also designed. This ammunition also served the M1911 pistol adopted by the Army in 1911.

The .45 GAP is a variant of the regular .45 cartridge, designed on behalf of Glock for more compact handguns.