PSA - Don't shoot .40 S&W in a 10mm gun!

[ZeSpectre]

Guy at the range last night had a brand new 10mm and was asking if he could also shoot .40 S&W in it. I was going to stay out of the issue until I heard a couple of folks say "sure don't see why not".

PUBLIC SAFETY ANNOUNCEMENT! Auto cartridges headspace on the mouth not the rim, firing .40 S&W in a 10mm gun is a BAD IDEA.

for more info see this article http://www.thegunzone.com/10v40.html

This ends this public safety announcement.

(EDIT: This refers to Semi-Automatic pistols. If you use moonclips in a revolver you are fine)

 

[renegade1alpha]

In an auto, yes this is a bad idea! But in a revolver such as the S&W Model 610 10mm you can shoot S&W .40 ammo using moon clips. Its the same as shooting .22 shorts in a .22 long rifle revolver.

 

[General Geoff]

Yeah, can't do it with brass chuckers.

Smith & Wesson 610 revolver is fine with moon clips.

 

[scrat]

So Zespecrte what happened did the guy try to do it. Or not. Hopefully not.

 

[ZeSpectre]

So Zespecrte what happened did the guy try to do it. Or not. Hopefully not.

No he didn't. I pointed out why (headspace issue) and everyone present agreed that it would be a bad idea.

 

[Zoogster]

Yes it is a very bad idea and could lead to significant problems.

I however have seen people successfuly get away with it because the cartridge can and often does headspace on the extractor. So they are gambling with thier safety with risk of a kaboom, likely to ruin the extractor with excessive wear etc but can get away with it sometimes.

What that means is there may be individuals who have done it and report that things were fine firing off entire magazines even though it should not be done.
An extractor was never meant to reliably headspace a cartridge, and so it is only a matter of time.

 

[648E]

My neighbor just got a new 10mm Kimber Custom II (?) and a guy who "knows alot about guns" told him he could fire .40 S&W in it with a different operating spring.

I told him this was probably not a good idea, and I KNOW it's a bad idea with the 10mm GLOCKS, I have a G29. Not knowing enough about 1911's I couldn't say with 100% certainty that it's not acceptable, but I think I will print the article linked above for him.

 

[DragonFire]

Even after reading the link, I guess still I don't see where the "risk of a kaboom" comes in.

The most likely event will be that the firing pin doesn't extend far enough to set off the round. If it does set off the round, the brass will suffer, gun will get dirty (from the lack of sealing of the case), maybe break the extractor, and possibly lousy accuracy. But where's the danger?


Not that I recommend doing it, but there's lots of things I don't recommend doing that aren't danerous. I've seen 9's and 357sig's shot in a 40, and I accidently shot 10mm out of a 45 (revolver using moonclips). No reason why I'd do it again, but nothing to write home about either.

 

[ZeSpectre]

Even after reading the link, I guess still I don't see where the "risk of a kaboom" comes in.

Look it's really simple, In trying to be helpful I've issued a "this is not safe and may cause damage/injury" warning, I've said why, and I've posted some backing information.

If you (or anyone else) wants to go ahead and do it anyway that's your decision to make 'cause I'm neither your parent nor your babysitter and I'm not gonna argue with a fencepost. For those of you who can take "a word to the wise", well there it is.

 

[General Geoff]

357sig's shot in a 40, and I accidently shot 10mm out of a 45 (revolver using moonclips).

Both of these instances are EXTREMELY dangerous, as .357 Sig has a higher pressure rating than .40. And 10mm out of a .45, be very very glad you didn't suffer a kaboom there. The space around the bullet in the chamber/barrel probably saved your life, in both of these cases.

 

[Zoogster]

Both of these instances are EXTREMELY dangerous, as .357 Sig has a higher pressure rating than .40. And 10mm out of a .45, be very very glad you didn't suffer a kaboom there. The space around the bullet in the chamber/barrel probably saved your life, in both of these cases.

This is very true (though I would have said danger, many people lose chunks of thier face, or hands and do not die from kabooms.)
The .357Sig is actualy a necked down .40S&W, so since you fired it in a .40 barrel the pressures did not reach what they are designed to operate at. Not smart but I am not surprised nothing harmed you there. Horrible chamber support, but also horrible pressure buildup (meaning the round was also at a significantly lower velocity than rated for.)

As for the 10mm in a .45, the operating pressures are extremely different and that was very dangerous. Even though the .05 wasted space all around the cartridge meant it got nowhere near the pressures or velocity the 10mm round is designed to work at, it still had next to no case support. That lack of case support could still burst the case even at lower pressures.

As I mentioned you also achieved awful velocity on those rounds because the pressure escaped into the extra barrel and chamber space as well as around the bullet going down the barrel rather than being concentrated behind the bullet. So it was pointless. It wasn't like firing those calibers at all.



A .40S&W and 10mm are however the same diameter chamber and barrel. So the pressures will reach what they are designed to reach. If for some reason the extractor does not headspace the cartridge far enough (and it is not designed to headspace) or the back of the cartridge slips past the extractor, to rest where a 10mm round is supposed to then there will not be enough case support on significant weak forward portions of the brass. That is a reciped for a kaboom.
So whether it happens because the extractor was damaged on the previous shot, the model firearm has an extractor it does not headspace on, or it simply slips passed the extractor to rest on the breech face like the proper round is supposed to, it is all a recipe for danger.

 

[tunnug]

most of the confusion comes from being able to buy .40S&W barrels for 10mm guns to be able to shoot the .40's but people that don't know (or know everything) will say "oh,yeah- you can shoot .40's in a 10mm"without realizing what it takes.

 

[RyanM]

Look it's really simple, In trying to be helpful I've issued a "this is not safe and may cause damage/injury" warning, I've said why, and I've posted some backing information.

I don't think this guy was trying to be belligerent.

Where is the risk of a kaboom? .40 is 35,000 PSI max, 10mm is 37,500 PSI. 10mm also holds more powder. If the round is headspaced improperly because it's only held by the extractor, it's gonna headspace too deep, not too shallow, thus a partially unsupported chamber won't be an issue.

Yes, firing .40 in a 10mm is a bad idea. Yes, it might damage your extractor. Yes, it might not cycle the gun.

But can it actually cause a k/b?

 

[ZeSpectre]

I don't think this guy was trying to be belligerent.

Possibly not but he's being willfully stupid when he reads the article where the author got the rounds to go off every time and then he posts the following statement...

The most likely event will be that the firing pin doesn't extend far enough to set off the round.

:banghead:

it's gonna headspace too deep, not too shallow, thus a partially unsupported chamber won't be an issue.

The slide moving forward picks up the round and presses it against the breech face thus shoving it into the chamber. The round may bounce foreward but the extractor (now pressing on the CASE not catching on the RIM holds the round back. (Picture a shotgun held loosely to your shoulder) That's what the extractor is doing to a .40 round. Now touch that off.

The round slams back against the breechface and firing pin HARD, Like a loosely held shotgun would to your shoulder.

This might or might not expose more case and create an unsupported case situation and thus KABOOM (okay it might not but WHY would you take that chance?)

Even if it doesn't do that the case is going to batter back and forth beating the hell out of the breech face, the firing pin, and the extractor. The extractor is also going to suffer from being pressed outwards by the wider CASE not by the rim space where it's supposed to fit.

Again, why do it?

 

[rcmodel]

ZeSpectre nailed it!

Gun battering is the result, because the .40 case only head-spaced by the extractor hook, gets a running jump-start before it slams into the breach-face every shot.

rcmodel

 

[g.willikers]

If memory serves, it was possible to use the shorter 9mm ammo in 1911s designed for .38 super. The barrels had kind of a half shoulder around the top of the chamber entrance that caught the cases by the rim.
A fellow in our club said he used to do that a lot due to the difference in ammo prices between the two calibers and never had a problem.
Anyone else ever heard of this?

 

[atblis]

Springfield Omega is okay with 40.

 

[DragonFire]

I don't think this guy was trying to be belligerent.

I don't see where I was belligerent. I don't see where I said anyone was wrong, or that it wasn't a bad idea or anything but ask where people saw the danger. I also don't see why cetain people had a snit with anything I said.

Gun battering is the result,

gun battering isn't dangerous unless you let the gun get so battered that it's unsafe.

This might or might not expose more case and create an unsupported case situation and thus KABOOM (okay it might not but WHY would you take that chance?)

Still seems like alot of IFs. IF the case hangs up on the extractor, and the firing pin sets it off, and the case flies back hard enough to push itself out of the barrel to expose more case (which would have to push the gun out of battery, wouldn't it).


Like I said, I still don't think it's something you'd want to do, but I still don't see it as a huge risk.

But if ZeSpectre wants to warn people about it, fine. I'll look forward to him warning us all about the dangers of reloading, and of shooting after a misfire and ...

 

[ZeSpectre]

Well if I sounded in a snit then I apologize.
I am however pretty amazed that you say you went to the link and saw the evidence and are still making a case that it's "not a huge risk".

gun battering isn't dangerous unless you let the gun get so battered that it's unsafe.

And with that I think I'm just going to go my way and you can go yours.

 

[jonmerritt]

It seems like a good idea to only use the ammo type the manufacturer says that will work correctly

 

[RyanM]

The round slams back against the breechface and firing pin HARD, Like a loosely held shotgun would to your shoulder.

Hm, didn't think of that. That probably would be bad. After all, revolvers tend to allow rounds to rattle back and forth, and Sam Colt decided, for some mysterious reason, to add a topstrap when he designed a cartridge revolver from the ground up. Maybe the conversions and open tops were wearing out too fast.