.25 ACP
.25 ACP cartridge with scale
Type	Pistol
Place of origin	United States and Belgium
Production history
Designer	John Browning
Designed	1905
Produced	1905–present
Specifications
Case type	Semi-rimmed, straight
Bullet diameter	.2512 in (6.38 mm)
Land diameter	.2429 in (6.17 mm)
Neck diameter	.276 in (7.0 mm)
Base diameter	.278 in (7.1 mm)
Rim diameter	.302 in (7.7 mm)
Rim thickness	.043 in (1.1 mm)
Case length	.615 in (15.6 mm)
Overall length	.910 in (23.1 mm)
Rifling twist	1:16
Primer type	Pocket pistol
Maximum pressure	25,000 psi (170 MPa)
Maximum CUP	25,000[1] CUP
Ballistic performance
Bullet mass/type Velocity Energy 35 gr (2 g) JHP 900 ft/s (270 m/s) 63 ft⋅lbf (85 J) 45 gr (3 g) JHP 815 ft/s (248 m/s) 66 ft⋅lbf (89 J) 50 gr (3 g) FMJ 760 ft/s (230 m/s) 65 ft⋅lbf (88 J)
Test barrel length: 2" Source(s): Guns & Ammo Magazine

The .25 ACP (Automatic Colt Pistol), also known as the .25 Auto, .25 Automatic, or 6.35×16mmSR) is a semi-rimmed, straight-walled centerfire pistol cartridge introduced by John Browning in 1905 alongside the Fabrique Nationale M1905 pistol.

Design

The cartridge is of semi-rimmed design meaning that the rim protrudes slightly beyond the diameter of the base of the cartridge so the cartridge can headspace on the rim.^[2]

Though the .25 ACP was designed for semi-automatic pistols, various .25 ACP revolvers were produced in the early twentieth century by Belgian, French, and German gunmakers such as Adolph Frank and Decker.^[3] In the late twentieth century, Bowen Classic Arms produced a custom Smith & Wesson revolver in .25 ACP.^[4]

Performance

The use of the .25 ACP allows for a very compact lightweight gun, usually pocket pistol. With quality ammo available on the market, the .25 ACP is viewed by some^[who?] as a solid choice for personal defense handguns due to its centerfire-case design, which is inherently more reliable than a .22 LR rimfire cartridge.^[5]

• 
  FN 1905/6
• 
  Modern jacketed hollow point loads for 6.35mm/.25 cal.
• 
  The Walther Model 9 pistol uses 6.35mm
• 
  Bauer .25 Auto pocket pistol
• 
  Raven MP-25 .25 ACP chrome with faux mother of pearl grips and push up safety