10MM = .40"Auto Magnum

.40" AUTO MAGNUM. - Oh all right, - the 10MM Auto.

Col. Jeff Coopers 'brainchild' the 10MM Auto is my all time favorite pistol round – being powerful, flat-shooting and versatile. It is good enough to use as a hunting caliber on short range game, and works well as a carbine load, as do the rimmed case .357" Magnum and .44" Magnum. - But the 10MM seems to be hanging back at the rear of the popularity field instead of leading as it should.

There was a long list of failings by organisations that no doubt had a negative effect on the 10MM when it was introduced – The first auto built for it in 1983, The BREN TEN ran into production problems almost immediately, leading to quality issues, defaulted pre-production orders, guns being supplied without magazines, and eventual bankruptcy after only three years. Colt took-up the baton and built the Colt Delta Elite that was an adaptation of the old M1911 design. The FBI tried the 10MM Auto in a M1911 and in the Thompson 1928 sub-machine gun before selecting the Smith & Wesson model 1076 in 1990 and contracted with Heckler & Koch for MP5/10 sub-machine guns. Shortly after they decided that the full power 10MM was too much gun for lighter built agents and specified the 10mm Lite loading, which is also said to have lead to S&W designing the .40"S&W. - However, there are reports that those early handguns built for the 10MM Auto round weren't up to coping with the powerful recoiling cartridge when repeatedly fired, and battered themselves to death.

GLOCK 20 10MM.

The arrival of the Glock 20 with fifteen round magazines and very manageable recoil saved the day for this modern cartridge originally made by FFV Norma AB. - Although I don't claim any particularly great handgun skills, - when my early prototype Glock 20 10MM landed I was rapt that it was as gentle, fast and easy to shoot as my first series G17 9mm.

HICKOK45 - Home on the range with 10MM.

 I ran the same IPSC action courses alternating between the two calibers and made the same times under Comstock Scoring - except the Glock 20 was working in Major Power Factor. I know some folk notice the larger grip of the G20 and G21(45ACP) – but personaly the big framed guns seem to fill my hands better.

                                                   10 MM Auto Cartridge.

I maintain that if this round had been called .40"AUTO MAGNUM right from the start by Col. Jeff Cooper it would have risen to the top despite being let-down by the early hardware. The two sweetest handling pistols that I've ever owned are the 10MM Glock 20 and the Smith & Wesson 610 Classic Revolver, - using full-moon clips that also work great with .40" S&W rounds.- We all know that 'real American men' prefer blonds and Magnums.

The bullet diameter actually is .40" - that's 10.16mm – not 10mm. (- If it did measure 10mm – that would be a .39")

A nice line-up of Pistol Rounds for comparison.

You will see that the .40" Auto Magnum - Oops, the 10MM - is a relatively long case - this gives plenty of room in the brass case to even load a duplex load using two 100gn 'truncated-cone' pills and to shoot "snake-eyes" at handgun ranges - I know this because I've done it -but that's another story !

Afterword: 

Greg Ellifritz is a full-time police training officer in central Ohio - he conducted and published a report on handgun calibers / effectiveness in police shootings (well worth reading). I asked him if he had any data on the 10MM - He replied that there wasn't enough to be meaningfully included - but that he had a friend with the *** in Afghanistan who carried a Glock 20 10MM and that he swore that it was most effective at penetrating and resolving issues with combatants in vehicles at road-blocks!

Does anyone else share my love of this powerful and flat shooting, versatile modern round?

Marty K.