10mm

10mm Auto
10mm Auto Jacketed Flat Point cartridge
Type	Pistol
Place of origin	United States Sweden
Service history
Used by	FBI Hostage Rescue Team FBI Special Weapons and Tactics Teams Slædepatruljen Sirius
Production history
Designer	Jeff Cooper FFV Norma AB
Designed	1983
Produced	Since 1983
Variants	.40 S&W 9×25mm Dillon 9×25mm Super Auto G .357 Sig
Specifications
Parent case	.30 Remington
Case type	Rimless Straight
Bullet diameter	C.I.P.: 10.17 mm (0.400 in) SAAMI: .4005 in (10.17 mm)
Neck diameter	C.I.P.: 10.74 mm (0.423 in) SAAMI: .423 in (10.7 mm)
Base diameter	C.I.P.: 10.80 mm (0.425 in) SAAMI: .425 in (10.8 mm)
Rim diameter	C.I.P.: 10.80 mm (0.425 in) SAAMI: .425 in (10.8 mm)
Rim thickness	C.I.P.: 1.40 mm (0.055 in) SAAMI: .055 in (1.4 mm)
Case length	C.I.P.: 25.20 mm (0.992 in) SAAMI: .992 in (25.2 mm)
Overall length	C.I.P.: 32.00 mm (1.260 in) SAAMI: 1.250 in (31.8 mm)
Case capacity	1.56 cm3 (24.1 gr H2O)
Rifling twist	406.40 mm (1 in 16 inches)
Primer type	Large pistol
Maximum pressure (C.I.P.)	230 MPa (33,000 psi)
Maximum pressure (SAAMI)	37,500 psi (259 MPa)
Ballistic performance
Bullet mass/type Velocity Energy 175 gr (11 g) STHP Winchester 1,290 ft/s (390 m/s) 649 ft·lbf (880 J) 180 gr (12 g) FMJ Federal 1,030 ft/s (310 m/s) 424 ft·lbf (575 J) 155 gr (10 g) TAC-XP Doubletap Ammunition 1,400 ft/s (430 m/s) 675 ft·lbf (915 J) 135 gr (9 g) Controlled Expansion Doubletap Ammunition 1,600 ft/s (490 m/s) 768 ft·lbf (1,041 J) 230 gr (15 g) Hardcast Solid Doubletap Ammunition 1,150 ft/s (350 m/s) 676 ft·lbf (917 J)
Test barrel length: 117 millimetres (4.6 inches) Source(s): DoubleTap Ammunition

The 10mm Auto (10×25mm, official C.I.P. nomenclature: 10 mm Auto, official SAAMI nomenclature: 10mm Automatic) is a semi-automatic pistol cartridge first developed by Jeff Cooper and introduced in 1983 with the Bren Ten pistol. Its design was subsequently improved, then produced initially by ammunition manufacturer FFV Norma AB of Åmotfors, Sweden.

Although it was selected for service by the Federal Bureau of Investigation in 1989 from the aftermath of the 1986 FBI Miami shootout, the cartridge was later decommissioned (except by the Hostage Rescue Team and Special Weapons and Tactics Teams) after their Firearms Training Unit eventually concluded that its recoil was excessive in terms of training for average agents' and police officers' competency of use and qualification, and that the pistols chambered for the cartridge were too large for some small-handed individuals. These issues led to the creation and following replacement to a shorter version of the 10mm that exists today as the .40 S&W. The 10mm never attained the mainstream success of this compact variant, but there is still an enthusiastic group of supporters who often refer to the .40 S&W as the ".40 Short & Weak" or "Short and Wimpy". The cartridge was originally known as the .40 Super.

The 10mm Auto cartridge was originally drafted and championed by eminent firearms expert Lieutenant Colonel John Dean "Jeff" Cooper. It was designed to be a medium-velocity pistol cartridge with better external ballistics (i.e., flatter trajectory, greater range) than the .45 ACP and capable of greater stopping power than the 9×19mm Parabellum. When FFV Norma AB (now Norma Precision AB) designed the cartridge at the behest of Dornaus & Dixon Enterprises, Inc. for their Bren Ten pistol (a newly developed handgun with design inspired by the CZ 75), the company decided to increase the power over Cooper's original concept. The resulting cartridge—which was introduced in 1983 and produced since—is very powerful, containing the flat trajectory and high energy of a magnum revolver cartridge into a relatively short, versatile rimless cartridge for a semi-automatic pistol. The case was derived from the .30 Remington rifle round, cut down and the walls straightened to accept the same diameter bullet as the much older .38-40 Winchester.