In the mid-1980s, Americans were clamoring for a medium-bore, high-velocity pistol cartridge. The 10 mm Auto was developed for the Bren Ten pistol and almost died with it when the gun’s maker encountered business difficulties. Colt literally rescued the cartridge from extinction with an M1911 variant called the Delta Elite. Early loadings of the 10 mm were very hot, but ammunition makers prudently learned to tone them down. Current loads are generally tame, but the hotter ones are about 30 percent more powerful than the .45 ACP. I well remember a handloading exercise with a Bar-Sto-barreled Delta. Careful sequential loading with top components at lower velocities produced the tightest pistol group I can recall. At 25 yards, 10 rounds went into 0.58 inches.

By 1996, American shooters were spending great time and effort on defense-based shooting sports that required a lot of attention to the power level, or kinetic energy, developed by a load. Since it was for competition, everyone wanted the lowest energy possible, as long as it made the major caliber floor. That’s because it was easier to shoot. Working with Winchester, Colt developed Government Models chambered for a new cartridge called the 9x23 mm Winchester. A brilliantly engineered cartridge, the 9x23 mm appears to be a 9 mm Luger case extended by 4 millimeters. It is actually much more than that, since the case web is specifically built to accept high pressures. For some reason, the 9x23 mm never really caught on and disappeared from the scene. It was exceptionally hot, driving a 124-grain, 0.355-inch bullet to almost 1,500 fps. I have reloading data from an impeccable source that goes well beyond that. Like the high-performance 10 mm Auto before it, the 9x23 mm produced stresses that were hard on the rugged M1911 platform and harder still on shooters unaccustomed to recoil and muzzle blast.

Smith & Wesson joined forces with Winchester Ammunition to produce one of the most popular new cartridges ever offered. In order to split the difference between the magazine capacity of the popular 9 mm guns and the decisive power of the big bores, the Winchester/S&W effort produced the .40 S&W in 1990. Colt had no real need to get into that business, so it chambered only a few M1911 models in that highly interesting caliber. In one of the “little” M1911s—Defender or Officer’s ACP—the .40 S&W starts to make some sense. Also, there are two different men in my circle of gun friends who have reported handling full-size Colt M1911s in .40 S&W.

That’s it—twelve chamberings—in just more than a century of M1911 gunmaking at Colt. The preceding listing is as complete and accurate as I can make it, but I concede the possibility that something was left out. In that regard, I know about the 9.8 mm Colt/9.65 mm Browning. I don’t consider that to be a true M1911 pistol. If anyone can tell me of other calibers originally chambered at Colt’s of Hartford in a true M1911, please write and tell me. I will ensure that shooters everywhere get the word.