From .45 ACP. (2009, April
28). In Wikipedia, The Free Encyclopedia. Retrieved 15:46,
May 6, 2009, from
"The .45 ACP (11.43x23mm Automatic Colt Pistol), also known as the .45 Auto by C.I.P., is a rimless pistol cartridge designed by John Browning in 1904, for use in his prototype Colt semi-automatic .45 pistol and eventually the M1911 pistol adopted by the U.S. Army in 1911.
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 of the
Philippine-American war, than the .45 Colt. The current issue rifle
at the time, the .30-40 Krag, also had failed to stop Moro
warriors; 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.
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 result from Colt was the Colt Model 1905 and the new .45 ACP. The original round that passed the testing fired a 200 grain (13 g) bullet at 900 ft/s (275 m/s), but after a number of rounds of revisions between Winchester Repeating Arms, Frankford Arsenal, and Union Metallic Cartridge, it ended up using a 230 grain (15 g) bullet at about 850 ft/s (260 m/s). The resulting .45 caliber cartridge, named the .45 ACP, was similar in performance to the .45 Schofield cartridge, and only slightly less powerful (but significantly shorter) than the .45 Colt cartridges the Cavalry was using. The cartridge case shared the same head dimensions as the .30-03 and later .30-06 rifle cartridges in use by the military at the time.
By 1906 bids from 6 makers were submitted, among them Browning's design, submitted by Colt. Only DWM, Savage, and Colt made the first cut. DWM, which submitted two Luger pistols adapted to the .45 ACP cartridge, withdrew from testing after the first round of tests, for unspecified reasons.One of the DWM pistols, serial number 1, was destroyed in testing; the remaining instance, serial number 2, is considered one of the most desirable collectors handguns in existence.
In the second round of testing in 1910, the Colt design passed the extensive testing with no failures, while the Savage design suffered 37 stoppages or parts failures. The resulting Colt design was adopted as the Model 1911."