Springfield's Ronin 1911
Handloader|February - March 2022
10mm Auto Handgun Loads
Patrick Meitin

I handled my first 10mm Auto while wild boar hunting behind hounds about 1990. The borrowed 1911 acted as backup during a bow hunt – which, it turned out, I would actually need. Those northern California boars were especially ill-tempered and dogs have a way of turning up the temperature. To make a rather long story mercifully short, at the end of a gruelingly long chase I stopped a full-on charge by pumping three quick 10mm slugs into the point-blank, grunting blob. The boar staggered onto its side only feet away. The 10mm Auto had lived up to its reputation as a serious thumper, on an animal that later pulled a ranch scale to 368 pounds gutted.

The 10mm Auto was designed by Whit Collins, John Adams and Irving Stone, with input from Jeff Cooper of Gunsite Academy fame. Cases were created by cutting down .30 Remington brass. The pistol was introduced in 1983 by the California company Dornaus & Dixon via the Bren Ten pistol, with Norma producing the factory ammunition. Dornaus & Dixon soon encountered financial problems, with Colt taking the baton in 1987 and introducing the 10mm Delta Elite on a beefed-up 1911 frame. For a short time, the FBI believed the 10mm was the answer to inadequacies demonstrated during the infamous 1986 Miami Florida shootout, where several agents were killed by bank robbers, who inflicted casualties after absorbing several shots from standard-issue handgun cartridges. Yet, it was soon discovered many agents couldn’t handle the 10mm Auto’s recoil.

The 10mm enjoyed a short period of popularity, which eventually waned, though the cartridge has always maintained a cult-like following with specialized segments of U.S. shooters, namely hunters. The cartridge is capable of cleanly taking deer- and hog-sized animals with well-placed shots. The cartridge seems to be enjoying a resurgence in popularity as of late.

The 10mm Auto handles any currently available .40-caliber bullet, including weights down to 135 grains pushed to nearly 1,600 feet per second (fps). Yet, 180- to 200-grain bullets help the 10mm shine. Two hundred-grain bullets sent at around 1,200 fps were the original 10mm Auto standard, though more recently 180s have become de rigueur, providing velocities up to 1,200-plus fps and delivering around 650 foot-pounds of muzzle energy – about 150/200 foot-pounds more than the .45 ACP. The 10mm includes 22 percent greater case capacity than the more popular .40 S&W. The 10mm includes a maximum pressure of 37,500 psi – about 7 percent higher than the 9mm Luger and .40 S&W. The high price of factory ammunition makes it a handloader’s cartridge.

AUTO PREREQUISITES

Like other rimless autopistol cartridges, the 10mm headspaces on the case mouth. This requires finishing rounds with a light taper crimp to hold the bullet securely but also provide proper head spacing. Maximum overall loaded length (OAL) is 1.26 to 1.27 inches. Heeding listed seating depths is vitally important, as seating bullets too deeply can introduce pressure spikes. The maximum case length is .992 inch – an important dimension due to headspace requirements. Trim-to specs are .982 inches, though most 10mm brass will likely require disposal due to wear before trimming becomes necessary. Segregate 10mm brass by length to realize top accuracy.

Some rules of thumb also apply. It is essentially impossible to glean any pressure information from the condition of fired primers, as even light loads eject brass with flattened primers. More importantly, when planning loads, bullet length becomes as important as weight. When seated to the required overall length for proper head spacing, heavier and/or longer bullets occupy more case space and raise pressures from a combination of added bearing surface or extra weight. This also means light-for-weight, lead-free bullets can require reduced load charges, just as with heavier lead bullets.

THE PISTOL

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