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.38 ACP
Type Pistol
Place of origin USA
Production history
Designer John Browning
Designed 1900
Manufacturer Colt
Case type Semi-rimmed, straight
Bullet diameter .356 in (Bad rounding hereScript error mm)
Neck diameter .384 in (Bad rounding hereScript error mm)
Base diameter .384 in (Bad rounding hereScript error mm)
Rim diameter .406 in (Bad rounding hereScript error mm)
Rim thickness .050 in (Bad rounding hereScript error mm)
Case length .900 in (Bad rounding hereScript error mm)
Overall length 1.280 in (Bad rounding hereScript error mm)
Primer type Small pistol
Ballistic performance
Bullet weight/type Velocity Energy
115 gr (Bad rounding hereScript error g) FMJ1,150 ft/s (Bad rounding hereScript error m/s)338 ft·lbf (Bad rounding hereScript error J)
125 gr (Bad rounding hereScript error g) JHP1,100 ft/s (Bad rounding hereScript error m/s)336 ft·lbf (Bad rounding hereScript error J)
130 gr (Bad rounding hereScript error g) FMJ1,040 ft/s (Bad rounding hereScript error m/s)312 ft·lbf (Bad rounding hereScript error J)
Source(s): Cartridges of the World[1]

The .38 ACP (Automatic Colt Pistol) also known as the .38 Auto was introduced at the turn of the 20th century for the Browning designed Colt M1900. The cartridge headspaces on the rim.[2] It had first been used in his Model 1897 prototype, which Colt did not produce. The metric designation for the round is 9×23mmSR (SR—Semi Rimmed) (not to be confused with the modern 9×23mm Winchester or the .380 ACP).


File:Colt M1900 AdamsGuns.jpg

Initial loadings of this cartridge were quite powerful. Reported ballistics for the first commercial loads were a 130-grain bullet at 1,260 ft/s (Bad rounding hereScript error m/s), and some experimental loads ran as high as 1,350 ft/s (Bad rounding hereScript error m/s).[3] However, these ballistics proved too violent for the Colt Model 1900 pistol, and velocities were soon lowered to below 1,200 ft/s (Bad rounding hereScript error m/s). Subsequent commercial loadings varied considerably in power. For example, Captain Hugh B.C. Pollard, writing in Automatic Pistols published in 1920, gives Winchester factory ballistics as a 130-grain bullet at 1,175 ft/s (Bad rounding hereScript error m/s) for 398-foot-pound-force (Bad rounding hereScript error J) of muzzle energy; for Ely ammo, the figures were a 128-grain bullet at 1,100 ft/s (Bad rounding hereScript error m/s) and 344-foot-pound-force (Bad rounding hereScript error J) and for Kynoch a 130-grain bullet at 1,000 ft/s (Bad rounding hereScript error m/s). (Part of the reason for the disparity may have been the result of the fact that the Winchester ammo was tested from a 6-inch (Bad rounding hereScript error mm) barreled Colt Model 1902 while the British loads were probably tested from the shorter-barreled Webley auto pistol in this caliber.) Later U.S. commercial loads in this caliber had factory standard ballistics of a 130-grain bullet at 1,040 ft/s (Bad rounding hereScript error m/s) from the 4.5-inch (Bad rounding hereScript error mm) barrel of the Colt 1903 Pocket Model.

The .38 ACP was jinxed by two factors: By the time the Colt autos in this caliber were introduced, Army Ordnance was already favoring a return to a .45 caliber sidearm, and the pistols themselves were soon rendered primitive and obsolescent in comparison to the Colt M1911. However, they did see small but steady sales up until the introduction of the more powerful .38 Super, which was little more than the .38 ACP loaded back to its original ballistics. In the interests of safety, American ammunition companies always loaded the original .38 ACP loads in brass cases, while .38 Super ammunition was loaded in nickel cases. Sales of .38 ACP ammo no doubt enjoyed a modest spike during the surplus gun boom of the 1950s and 1960s, since the cartridges would usually cycle in Spanish surplus pistols like the Astra 400 that were chambered for the 9mm Bergmann-Bayard (9mm Largo), despite the fact that the .38 ACP was semi-rimmed and slightly shorter than the rimless 9mm Largo. Some Astra 400 pistols were stamped "9M/M&38" on the barrel, denoting that the barrel was specifically designed to chamber both 9mm Largo and .38 ACP.

Europe would eventually favor the 9 mm Parabellum cartridge developed from the 7.65 mm Parabellum. The Luger was ballistically similar to the .38 ACP but utilized a smaller case and higher pressures. Browning himself was not done with 9 mm cartridges and would soon introduce the 9mm Browning Long (9×20mm) in 1903 and the .380 ACP (9×17mm Short) in 1908.

.38 ACP pistolsEdit


Even though .38 ACP and .38 Super are the same size, it is dangerous to use the more powerful .38 Super ammunition in a firearm intended for .38 ACP, as firearm damage may result.

See alsoEdit


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  2. Wilson, R. K. Textbook of Automatic Pistols, p.234. Plantersville, SC: Small Arms Technical Publishing Company, 1943.
  3. Article in the April 19, 1900 issue of Shooting and Fishing, quoted in Belden, C.T and Haven, A History of the Colt Revolver (1940)

External linksEdit

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