.45 ACP

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".45" redirects here. For the revolver cartridge, see .45 Colt. For the upcoming film, see .45 (film).

The .45 ACP (Automatic Colt Pistol, 11.43 x 23 mm ) 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 U.S. 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.

1 Design & History
2 Performance
3 Timeline
- 3.1 Muzzle velocity
4 Load variants
5 Synonyms
6 Firearms using the .45 ACP
7 See also
8 References
9 Further Reading
10 External links

[edit] Design & History

Image:45caliberACP.jpg

The U.S. 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 from Colt was .45 ACP, used on the Colt Model 1905. It was further developed and was tested 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. Image:45 ACP.jpg

The US Cavalry had been buying and testing various handguns in the late 1890s and early 1900s. The .45 Colt Single Action Army had largely been replaced, 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 those encountered in the Moro Rebellion warriors they were fighting at the time, than the .45 Colt. The current issue rifle at the time, the .30-40 Krag, also had failed to stop Moro warriors[1]; the British had similar issues switching to the .303 British, which resulted in the development of the Dum-dum bullet. 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 the replacement handgun. By 1906 bids from 6 makers 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 dispatching a wounded horse. 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.

[edit] Performance

Image:22-45.jpg 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, the increased material cost of manufacture compared to the 9 mm Parabellum cartridge, and lack of compliance with Standardization Agreements pertaining to handgun ammunition currently enacted between the US and many of its allies.

Even in its non-expanding full metal jacket (FMJ) version, the .45 ACP cartridge has a reputation for effectiveness against human targets because its large bullet creates a deep and substantial permanent wound channel, although modern scientific research and analysis of actual police shootings, such as the published work of Marshall and Sanow, has cast that reputation into doubt. Modern hollow-point configurations increase the expansion potential of the round, causing it to be significantly more effective.

Being a moderate-powered round on the energy scale, .45 ACP bullets have a decreased tendency to overpenetrate, which reduces the projectile's possibility of passing through the 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, although the resulting loss of magazine capacity, and the larger size and weight of pistols chambered in this caliber has led more police departments in the USA to adopt sidearms in .40 S&W, and .357 SIG.[2] Many US tactical police units still utilize the .45 pistol round, including the FBI's Hostage Rescue Team.<ref>Diez, Octavio. Special Police Task Forces.Lima Publications.40; Hogg, Ian. Jane's Gun Regonition Guide. 2nd Edition. Harper Collins Publishers. 113; Hopkins, Cameron. Most Wanted. American Handgunner, Jan 2000. </ref>

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.

[edit] 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.

[edit] 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)

[edit] Load variants

Several manufacturers market preloaded .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, increasing both the energy transferred from the round to the target and enhancing the wound creating power of the 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 higher velocity and more 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.