Dan wesson 10mm bobtail

Dan Wesson's Commander Classic Bobtail II

The 10mm Auto. Jeff Cooper's cartridge

By Joe D'Alessandro Editor | RealGuns.Com

I didn't know Jeff Cooper, and I'm not sure he would have liked me had we met. He was a serious gunner and combat expert, a genuine tough guy. Whereas, when I get an "owie" when working in my shop, my wife still applies a Mickey Mouse Band-Aid to make it all better. Some of Cooper's work was breakthrough, some of it retread. Some of it serious business, some of it puffery. A product of his creativity that outlived him, one I sincerely appreciate, is the 10mm Auto cartridge. The 10mm Auto is a round that offers more utility than a 1911 stuffed full of .45 ACP +P ammo. Where the 40 S&W is sort of like Jimmie Vaughan and the Fabulous Thunderbirds, the 10mm Auto is more like Stevie Ray and the best of "Double Trouble".

Case in point.

The 10mm Auto (center) has a case length of 0.992" and a maximum overall cartridge length of 1.260". That makes its case length 0.142" longer than that of the .40 S&W (right) and its overall cartridge length 0.125" greater. At 24.0 grains, the 10mm's case capacity is approximately 4 grains more than the 40 S&W.

In comparison to the .45 ACP (left), the 10mm auto case is 0.094" greater in length, however, the 10mm is 0.015" shorter in

overall cartridge length and the larger diameter .45 ACP case holds approximately 4 more grains of powder.

The 10mm gets its performance edge over the 40 S&W as a result of greater powder capacity, while its length, case and overall cartridge means the 10mm will function is a 1911 form firearm. The 10mm Auto is a rimless case that headspaces on its mouth with bullets secured with a taper crimp. The case takes a large pistol primer. Pictured is Starline brand brass, the type selected for my own handloads. The alloy is probably the same as other major brands, however, the heat treat tends to be different. Their brass seems more malleable and it seems to last longer.

Bullet points.

The 10mm Auto's bullet is 0.400" diameter for jacketed versions and 0.401" for cast, which means there are more types and weights available than most people will ever need. On a casual look, I found 65 brand, type and weight variations. There are full metal jackets for target work, frangible types for special circumstance self defense and jacketed soft and hollow points for self defense and hunting. Bullet weights range runs from 135 grains to 200 grains, with 180 grains arguably the most popular weight. Five bullet types were selected for this project that are a good representation of what might be selected as useful for the 10mm Auto shooter/handloader. They appear on the table in the L-R order they appear in the picture below the table.

Category: Bobtail

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