CALIBER

The "10mm" refers to the diameter of the bullet: 10 millimeters, or roughly .40 caliber. It is also commonly referred to as 10mm Auto, which is the full cartridge designation. You may also hear it called "10 milly" among enthusiasts.

The 10mm excels in hunting and outdoor defense situations. It is an especially strong choice for those needing protection from large animals like bears or mountain lions. It is available in both self-defense and hunting loads, and because of its slightly smaller diameter compared to .45 ACP, it can allow one or two extra rounds.

A 10mm 1911 is a pistol built on the classic 1911 platform but chambered in 10mm Auto rather than the traditional .45 ACP. Rock Island Armory offers several 10mm 1911 models, including the ROCK Ultra FS 10MM, the TAC Ultra FS 10MM, and the PRO Ultra Match 6" HC "Big Rock" 10MM, among others.

Yes. The 10mm Auto is considered the most powerful of the mainstream semi-auto rounds, with power levels on par with or exceeding the .357 Magnum. It delivers faster velocity, more penetration, and more energy than both the 9mm and .45 ACP. A typical 10mm load produces a muzzle velocity of 1,008 fps and muzzle energy of 406 ft-lbs, compared to the .45 ACP's 840 fps and 368 ft-lbs.

The 10mm offers higher velocity and energy, while the .45 ACP delivers a heavier, slower-moving bullet with greater diameter expansion. The 10mm bridges the gap between the 9mm and .45 ACP, offering more mass and more velocity, especially for scenarios where deeper penetration matters. For a full ballistics breakdown, see the 10mm vs. .45 ACP comparison at news.armscor.com/ballistics-showdown-comparing-the-power-of-10mm-vs-45-acp.