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The .45 ACP (Automatic Colt Pistol) pistol cartridge was designed by firearms designer John Browning. The .45 ACP was developed in 1905 for a prototype Colt pistol, which evolved into the M1911 pistol adopted by the US Army in 1911. The round would become one of the most successful cartridges of all time, among both military and civilian users. It has been used in innumerable handguns and submachine guns since its introduction.

Design & History

The Army had been using .38 caliber revolvers, and tested .38 caliber pistols developed by Colt just after the turn of the century. A larger round was requested of caliber not less than .45, and the result was from Colt was .45 ACP, used on the Colt Model 1905. It was further developed and went against several entrants in competitions for a new handgun, primarily DWM, Savage, and Colt (after 1907 tests). DWM dropped out, and the Colt performed better than the Savage during tests in 1910. The .45 ACP round entered U.S. military service with the adoption of the M1911 sidearms.

The US Cavalry had been buying and trying various handguns in the late 1890s and early 1900s. The .45 Colt Single Action Army had largely been replaced, and even by some double action versions of the same. The Cavalry had fielded some double action revolvers in .38 Long Colt, and they determined that the .38 caliber round was significantly less effective against determined opponents, such as the Moro warriors they were fighting at the time, than the .45 Colt (The current issue rifle at the time, the Krag, also had failed to stop Moro warriors so one is left to wonder if a mere handgun in any caliber would have been effective against them). This and other tests with calibers lead the Army, and the Cavalry to decide that a minimum of .45 caliber was required in the replacement handgun (via the Thompson-LaGarde Tests in 1904). By 1906 bids from 6 makes were submitted, among them the .45 ACP design from Colt.

It had also been determined that a .44-caliber bullet was the smallest diameter suitable for putting a wounded horse out of its misery. Colt had been working with Browning on a .41 caliber cartridge in 1904, and in 1905 when the Cavalry asked for a .45 caliber equivalent, Colt modified the pistol design to fire a .45 caliber version of the prototype .41 caliber round. The original round that passed the testing fired a 200 grain (13 g) bullet at 900 ft/s (275 m/s), but was later changed to a 230 grain (15 g) bullet at about 850 ft/s (260 m/s). The resulting .45 caliber cartridge, named the .45 ACP, is similar in performance to the .45 S&W cartridge, and only slightly less powerful (but significantly shorter) than the .45 Colt cartridges the Cavalry was using. Modern propellants have boosted the .45 ACP well beyond the power and velocity of the original .45 Colt, though modern .45 Colt loads are also far beyond the original loadings.

Performance

The result is one of the world's more effective combat pistol cartridges, one that combines very good accuracy and stopping power for use against human targets. The cartridge also has relatively low muzzle blast and flash, as well as moderate recoil. Like most pistol cartridges, it is a low-velocity round, and thus not effective against body armor. Another drawback for large-scale military operations is the cartridge's large size, weight and greater material costs in manufacturing compared to the 9 mm Parabellum cartridge.

Even in its full metal jacket (FMJ) form, the .45 ACP cartridge has a reputation for effectiveness against human targets because its large bullet creates a deep and substantial permanent wound channel. Hollow-point configurations increase the expansion potential of the round, causing it to be even more deadly.

Being a moderate-powered round on the energy scale, .45 ACP bullets have little tendency to overpenetrate, which otherwise results when a projectile passes through an intended target with enough velocity to injure another person. The combination of stopping power and controlled penetration makes the .45 ACP practical for police use. Many US hostage rescue teams prefer the .45 ACP because of these qualities.

Today most of the U.S. military uses the 9 mm Parabellum cartridge, but the accuracy of the .45 ACP cartridge has ensured its continued popularity with large caliber sport shooters. Many US Special forces and police units still use this round in the form of modified 1911A1s and Heckler & Koch's SOCOM Mk. 23s and USP Tacticals.

Timeline

  • 1899/1900 self-loading pistols test: Colt M1900 of .38 caliber entered
  • 1904 Thompson-LaGarde Tests: Caliber of new handgun should be at least .45
  • 1906-1907 handgun trials: Colt enters with .45 ACP design
  • 1910 final tests: Colt design out-performs Savage
  • On March 29th, 1911 the Colt design is officially adopted- and with it .45 ACP.

Muzzle velocity

  • 14.7 g (230 gr) Full Metal Jacket: 260 m/s (860 ft/s)
  • 11.9 g (185 gr) CCI/Speer Gold Dot JHP (from 5in (127 mm) barrel): 317 m/s (1041 ft/s)
  • 14.7 g (230 gr) Federal Hi-Shok JHP (from 5 in (127 mm) barrel): 260 m/s (860 ft/s)

+ P loads

  • 11.9 g (185 gr) JHP: 350 m/s (1150 ft/s)
  • 14.7 g (230 gr) JHP: 290 m/s (950 ft/s)

Load variants

Several manufacturers market pre-loaded .45 ACP rounds in sizes ranging from 117 to 230 (90 in the case of Le mas RBCD) grains (8 to 15 g), with the most popular commercial load being the standard military loading of a 230 grain (15 g) FMJ bullet at around 850 ft/s (260 m/s). Specialty rounds are available in weights under 100 grains (6.5 g) and over 260 grains (16.8 g); popular rounds among reloaders and target shooters include 185 and 230 grain (12 and 15 g) bullets. Hollowpoint rounds intended for maximum effectiveness against live targets are designed to expand upon impact with soft tissue, both increasing the energy transferred from the round to the target and enhancing the wound-creating power of the expanded round.

Most ammunition manufacturers also market what are termed "+P" loadings in pistol ammunition, including the .45 ACP. This means the cartridge is loaded to a somewhat higher maximum pressure level than SAAMI standard, generating more velocity and muzzle energy. This a common practice for updating older cartridges to match the better quality of materials and workmanship in modern firearms.

The terminology is generally given as ".45 ACP +P", "9 mm Luger +P", ".38 Special +P", etc., and appears on the headstamp. It is important to note that +P cartridges are dimensionally identical to standard-pressure one and will chamber and fire in all firearms designed for the standard-pressure loadings. +P loadings should not be used in firearms not specifically designed for them as they are harder on the gun and may cause damage and injuries.

Synonyms

  • .45 Auto
  • 11.43 x 23 mm

Firearms using the .45 ACP

See also

External links

Pistol and rifle cartridges

.45 ACP | .45 ACP | .45 ACP | Nabój .45 ACP | .45 ACP

 

This article is licensed under the GNU Free Documentation License. It uses material from the ".45 ACP".

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