.45 ACP

.45 ACP
.45 ACP cartridge full metal jacket
Type	Pistol
Place of origin	United States
Service history
Wars	World War I – present
Production history
Designer	John Browning
Designed	1904
Produced	1905–present
Variants	.45 ACP +P, .45 Auto Rim, .45 Super, .460 Rowland
Specifications
Case type	Rimless, straight
Bullet diameter	.452 in (11.5 mm)
Land diameter	.442 in (11.2 mm)
Neck diameter	.473 in (12.0 mm)
Base diameter	.476 in (12.1 mm)
Rim diameter	.480 in (12.2 mm)
Rim thickness	.049 in (1.2 mm)
Case length	.898 in (22.8 mm)
Overall length	1.275 in (32.4 mm)
Case capacity	25–27.4 gr H2O (1.62–1.78 cm3)
Rifling twist	1 in 16 in (406 mm)
Primer type	Large pistol LP (some makers are now using small pistol SP)
Maximum pressure (CIP)	19,000 psi (130 MPa)
Maximum pressure (SAAMI)	21,000 psi (140 MPa)
Ballistic performance
Bullet mass/type Velocity Energy 230 gr (15 g) FMJ, Winchester 835 ft/s (255 m/s) 356 ft⋅lbf (483 J) 165 gr (11 g) Hydra-shok, Federal 1,060 ft/s (320 m/s) 412 ft⋅lbf (559 J) 230 gr (15 g) FMJ, Double Tap 960 ft/s (290 m/s) 471 ft⋅lbf (639 J) 185 gr (12 g) JHP +P, Underwood 1,200 ft/s (370 m/s) 592 ft⋅lbf (803 J) 90 gr (6 g) TFSP, RBCD 2,036 ft/s (621 m/s) 829 ft⋅lbf (1,124 J)

The .45 ACP (Automatic Colt Pistol), also known as .45 Auto, .45 Automatic, or 11.43×23mm^[1] is a rimless straight-walled handgun cartridge designed by John Moses Browning in 1904, for use in his prototype Colt semi-automatic pistol. After successful military trials, it was adopted as the standard chambering for Colt's M1911 pistol.^[2] The round was developed due to a lack of stopping power experienced^[3] in the Moro Rebellion in places like Sulu. The issued ammunition, .38 Long Colt, had proved inadequate, motivating the search for a better cartridge. This experience and the Thompson–LaGarde Tests of 1904 led the Army and the Cavalry to decide that a minimum of .45 caliber was required in a new handgun cartridge.

The standard-issue military .45 ACP round uses a 230 gr (15 g; 0.53 oz) round-nose bullet at approximately 830 ft/s (250 m/s) fired from a government-issue M1911A1 pistol. It operates at a relatively low maximum chamber pressure rating of 21,000 psi (140 MPa), compared to 35,000 psi (240 MPa) for both 9mm Parabellum and .40 S&W, which due to a low bolt thrust helps extend the service lives of weapons. Since standard-pressure .45 ACP rounds are subsonic when fired from handguns and submachine guns, it is a useful caliber for suppressed weapons to eliminate the sonic boom.