The Rise and Fall of the 10mm Cartridge

In 1983, 10mm ammo was introduced by Lieutenant Colonel John Dean “Jeff” Cooper. Cooper is a firearms experts that has worked with high-level organizations including the FBI, Norma, and Smith & Wesson. His intention was to replace the .45 ACP with a more powerful round.

Cooper joined Whit Collins, John Adams, and Irving Stone, cut down a .30 Remington shell, and loaded it with a .40 caliber bullet. The group created a flatter trajectory and better transfer of energy in a bullet small enough to be used in a semi-automatic pistol.

A 10mm bullet measures 10.17mm, housed in a rimless, straight-walled casing. The case is .992 inch long. The Permanent International Commission for the Proof of Small Arms (C.I.P.) measures the round slightly over 1.260 inches.

The ammo weighs more than 9mm with an average of 135-200 grains. Hollow points are the most popular style.

Law Enforcement

Law enforcement used a .45 ACP round in the 1980s until there was a need for a stronger caliber. In 1986, there was a shootout in Miami wherein two FBI special agents were killed and 5 were wounded.  Eight FBI agents confronted two suspected bank robbers. The agents were armed with .38 Special revolvers, 12-gauge shotguns, 9mm semi-automatic pistols, and .357 Magnum revolvers. Around 145 shots were fired in under five minutes, 18 shots made contact with the suspects.

The FBI launched an investigation regarding the result of the shootout. Investigators determined that the agents’ semi-automatic weapons had adequate stopping power, but didn’t hold enough ammunition to be effective in the shootout.

Agents called for more firepower. Field tests were run on 10mm ammo and it was approved as standard issue for agents. One complaint was that there was too much recoil for some agents, so the power was reduced. 10mm ammo was quickly replaced by the .40 S&W, but this did not significantly affect the round’s popularity. It continues to be used by the FBI’s Hostage Rescue Team (HRT), Special Weapons and Tactics (SWAT) Teams, and law enforcement agencies throughout the U.S. The cartridge is used often for self-defense, hunting, and tactical use.

The 10mm’s Steep Climb

After the Miami shootout, there was a rush to manufacture 10mm ammo. The ammo was released, but not appropriately field tested in the Bren Ten pistol. The gun experienced malfunctions. The ammo was high pressure and caused the gun to lose accuracy.

Gun owners shied away from the ammo. The 10mm suffered a second blow when Dornause and Dixon Enterprises went bankrupt after producing only 1500 Bren Ten handguns.

An unlikely source saved the cartridge. Sonny Crockett, the fictional lead detective of TV’s Miami Vice, used a Bren Ten on the show. Crocket never had any malfunctions. Though the pistol failed to thrive; the ammo is still in demand. You can easily find 10mm ammo for sale. Cheap 10mm ammo is readily available in bulk from many websites.

Performance and Usage

Although the FBI has replaced the 10mm with the .40 S&W, it remains a worthy firearm. Its velocity ranges from 1,300 to 1,600 FPS, muzzle energy exceeds 750 ft.lbs., and it retains higher energy at 100 yards than many .45 ACP rounds.

Devoted followers accept the heavy recoil in exchange for performance and accuracy. Gun users prefer the round for a self-defense weapon. Hunters choose 10mm ammo for hunting white tailed deer and other game. In Denmark, hunters protect themselves from polar bears.

Users include:

  • Law enforcement agencies such as the Weimar Police Department, Plano Police Department, Coconut Creek Police Department, and the San Francisco Bay Area Rapid Transit (BART) Police Department.
  • The FBI Hostage Rescue Team
  • Special Weapons and Tactics Teams
  • Government of Denmark
  • Greenland’s Slædepatruljen Sirius (Sirius Sledge Patrol)
  • Ted Nugent, American musician and weapons enthusiast, he’s so loyal to 10mm ammo that he helped to create a custom Glock G40 10mm named the NUGE/TMT Tactical. Only 100 guns are in existence.