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.40 S&W or 10mm

887 Views 26 Replies 13 Participants Last post by  tedwitt
Lately I've seen references to 10mm handguns. However, I no longer see references to .40S&W. The .40S&W is the same as a 10mm bore, a short 10mm Magnum. For a while there were references & writings about the 10mm Magnum, but I seldom see this term used anymore. Is the present use of 10mm the same as a .40S&W, or is it still the 10mm Magnum?
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Ya, I wern't born last night, just curious!!馃榿馃榿馃榿
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The shorter 40S&W cartridge is held in place by the extractor. Shorter-cased 10mm rounds are also held in place by the extractor, so technically, it's not fully headspacing on the case mouth.
I have never owned a 10mm but my semi educated guess to that question would be NO! The reason for that answer is only a guess BUT since both the .40 and the 10mm are rimless cases, don't they headspace on the mouth of the brass? If my thinking is so, then wouldn't the .40 S&W cartridge drop down about a quarter of an inch into the chamber of a 10 mm.
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You could but you should not. The extractor will likely hold the 40 firmly enough to function for a while. It will wear quickly and lead to malfunctions. Another aspect is that it is not quit the same as shooting a shorter cartridge out of a revolver that uses a rimmed cartridge. In the revolver the chamber is uniform until the exit point. On a round that is designed to headspace on the cartridge case mouth there is of course step up or ledge in the chamber that the case mouth should set firmly against. With the firing of a shorter cartridge that ledge is subject to flame cutting or erosion. If done enough you will compromise the function of the pistol when used with the cartridge it was designed to use.
Will you have a catastrophic failure resulting in injury or death .....probably not. If I was in your shoes I would sell or trade the 40S&W rounds and get the right cartridge for MY pistol.
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On a round that is designed to headspace on the cartridge case mouth there is of course step up or ledge in the chamber that the case mouth should set firmly against. With the firing of a shorter cartridge that ledge is subject to flame cutting or erosion. If done enough you will compromise the function of the pistol when used with the cartridge it was designed to use.
As I noted above, the case is .147" away from the correct headspace. Over an 1/8 of an inch off - That's a big gap!
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With the firing of a shorter cartridge that ledge is subject to flame cutting or erosion. If done enough you will compromise the function of the pistol when used with the cartridge it was designed to use.
Here's a 40S&W case in my XDM-10 chamber being withdrawn.
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I was only speculating about 10mm because I once owned a .357 Magnum and usually shot .38 in it at the range for cost, of course. But when I stored it loaded for defense I'd load it with JHP .357 rounds. I thought about having the same kind of flexibility between .40 and 10mm, but clearly it's not the same thing. I have a G27 and love it, and I would only ever buy a G29 (or any other 10mm) if I could run .40 through it.

I don't think I'd ever want to use 10mm as a defensive round (overpowered for defense use and way more recoil than .40 or 9mm). I just thought it might offer the versatility of using 2 kinds of ammo in a single firearm (much like .38 and .357, or being able to fire .22LR in a .22 Magnum). But from the responses in this thread AND from a reply I got from the Glock support team, the answer is an emphatic NO, do NOT fire .40s&w rounds in a 10mm Auto gun. So I'll keep my G27 and put any thoughts of 10mm out of my mind.
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I was only speculating about 10mm because I once owned a .357 Magnum and usually shot .38 in it at the range for cost, of course. But when I stored it loaded for defense I'd load it with JHP .357 rounds. I thought about having the same kind of flexibility between .40 and 10mm, but clearly it's not the same thing. I have a G27 and love it, and I would only ever buy a G29 (or any other 10mm) if I could run .40 through it.

I don't think I'd ever want to use 10mm as a defensive round (overpowered for defense use and way more recoil than .40 or 9mm). I just thought it might offer the versatility of using 2 kinds of ammo in a single firearm (much like .38 and .357, or being able to fire .22LR in a .22 Magnum). But from the responses in this thread AND from a reply I got from the Glock support team, the answer is an emphatic NO, do NOT fire .40s&w rounds in a 10mm Auto gun. So I'll keep my G27 and put any thoughts of 10mm out of my mind.
Yup, me too.
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