One of the constants in the firearms world is the debate over which caliber is best. As that debate usually rages in the .45 and 9mm crowds, the 10mm sits quietly in the corner. While many recognize the round, few understand it and its potential. Today we will take a deep dive into the 10mm round.
The 10mm Round – A Versatile Option
The 10mm Auto cartridge is one of the most versatile and powerful semi-automatic pistol rounds ever developed. The round was conceived in the late 1970s by legendary firearms expert Jeff Cooper. Cooper envisioned a semi-automatic handgun round that could deliver significantly more power and performance than the standard 9mm or .45 ACP. He was particularly focused on law enforcement and self-defense applications. He wanted a round with superior penetration, higher velocity, and greater stopping power. Ultimately, he wanted a pistol caliber capable of pushing a 200-grain bullet at 1,200 feet per second.
His passion led to a collaboration between the Swedish ammunition manufacturer Norma Precision and American firearms designers. In 1983, the 10mm Auto was officially introduced alongside the Bren Ten, a semi-automatic pistol developed by Dornaus & Dixon. The Bren Ten was heavily inspired by the CZ-75 design and was intended to showcase the power of the new round. Despite its impressive ballistics, the Bren Ten suffered from reliability and supply chain issues. The company producing it went bankrupt, and production ceased, leaving the 10mm round to languish in limbo.
FBI Miami Shootout
An event that would change 10mm history forever happened on April 11th, 1986. On that day a small group of FBI agents moved to arrest two violent criminals in Miami. The gun battle that ensued would change things forever. While the agents were able to make good hits, the criminals kept fighting. The suspects were eventually killed, but in the process two special agents died from their wounds, while five other agents were injured by gunfire. The incident is infamous as one of the most violent episodes in the history of the FBI. It is often studied in law enforcement training. The scale of the shootout led to the FBI searching for a more effective round.
After extensive testing, the agency adopted the 10mm Auto in 1989, chambering it in the Smith & Wesson Model 1076. While the round offered exceptional stopping power and penetration, it also had significant drawbacks. These included high recoil and difficulty in rapid follow-up shots. In short, FBI agents found it difficult to qualify on handguns tests with the 10mm round. To address this, the power of the load was reduced to decrease recoil. This still did not solve the problem, so the process was repeated.
The 10mm Becomes the .40 S&W
At the end of the adjustments, the round ceased to be a true 10mm. This new round became the .40 S&W, which quickly gained widespread adoption by law enforcement agencies across the United States. After that, the 10mm Auto faded from mainstream use, with manufacturers shifting focus to the .40 S&W, 9mm, and .45 ACP. Many firearm companies discontinued their 10mm-chambered handguns, and the cartridge seemed destined for obsolescence.
While the round saw a decline in law enforcement, the 10mm Auto found new life among civilian shooters. This was particularly true in the hunting communities. The round’s high velocity, deep penetration, and superior energy transfer made it an excellent choice for hunting and for defense against large predators, such as bears. The round is a popular backcountry protection option. The Danish Royal Navy Special Forces Long Range Patrol (Slaedepatruljen Sirius) carries the 10mm Glock 20 for protection against polar bears. According to reports they have had many successful stops on record. Because of this ongoing and growing interest, many firearms companies moved to get 10mm guns to market. Today we see many great options to choose from.
The 10mm Round
One of the biggest factors in the 10mm resurgence has been ammunition performance. Modern 10mm loads offer a range of power levels. They range from full-power hunting and self-defense rounds to lighter loads designed for target shooting and reduced recoil. With this, the 10mm has become more manageable. I am a fan of the 10mm round because of its performance. This is especially true in self-defense. When we talk about 10mm, the words stopping power have real meaning.
