S&W 40 in a 10mm Pistol?

[Flame Red]

Was at an IPDA shoot today and a gentleman was going thru the course using a 10mm EAA Witness, and doing rather well too. I said to him that I had not seen many people going thru the course running 10mm. He shocked me and said that neither was he! He was shooting S&W 40 thru it and had been doing so for years!

So what is the official word - is using 40 S&W in any 10mm ok? Is it kind of like running 38 specials thru a 357 Magnum Revolver - a perfectly acceptable practice?

I would like to try it as 40 S&W is so much cheaper than 10mm - for plinking. But I don't want to damage my Delta Elite :banghead:

 

[Soybomb]

You'll probably be fine, but it does headspace on the front of the cartridge and the extractor is all that would be holding the round against the breech. .38spl and other rimmed rounds uses the rim to achieve this and not the front of the cartridge.

I sure wouldn't do it, because the time you're unlucky and it KB's you'll be out a gun and maybe a little skin.

 

[hagar]

I have shot 40 S&W in my Glock 20 just to see what it would do. Shoots ok, but to a different point of aim. Would only do it again if absolutely necessary.

 

[Zundfolge]

If you want to shoot .40 out of your 10mm, buy a .40 barrel. Otherwise you're risking catastrophic failure (at the very least it can't be good for the chamber).

My guess is that the guy bought a .40 barrel and dropped it into his 10mm.


Also you're going to need to change the recoil spring to a lighter one or it might not feed correctly.

 

[Stevie-Ray]

Does it extract OK? Seems like it wouldn't as the the case head is a smaller diameter than the 10. I'd be afraid of the extractor letting go of a 40. Also the erosion on the chamber couldn't be good.

 

[Sundles]

Shooting 40 S&W in 10mm chambers.

Ive done this some. I dont recommend it. While it worked just fine in both my 1911 type 10mm's, the 40 brass showed signs of high pressure--probably due to the fact that the 40 brass is so short in that long 10mm chamber, that the bullet jumps too far before engaging the rifling and thus the rifling starts to act as a bore obstruction and raises pressures.

I would only fire 40 S&W in 10mm chambers under emergency situations.

 

[grendelbane]

I do it all the time in my 610!

I don't recommend it in an auto pistol however. Most of the time you will probably get away with it. Not really worth taking the chance, however.

 

[Ohen Cepel]

I wouldn't do it in a pistol. Revolver, sure.

It might not damage the pistol but I wouldn't push my luck (I have bad enough luck as it it

 

[atblis]

Well

He probably omitted the minor detail that he purchased the conversion barrel from EAA for what? $80.

 

[Dobe]

Ive done this some. I dont recommend it. While it worked just fine in both my 1911 type 10mm's, the 40 brass showed signs of high pressure--probably due to the fact that the 40 brass is so short in that long 10mm chamber, that the bullet jumps too far before engaging the rifling and thus the rifling starts to act as a bore obstruction and raises pressures.

Just an assumption, but I believe the headspace in being kept in partial check by the extactor. I say partial, because there is some amount of wiggle room between the rim and the extractor. I think any gap between the bolt face and the primer is what is causing the high primers, and not the "free bore" jump to the rifling. Generally, the free bore will reduce pressure, not increase the pressure curve.

My biggest concern would be a future extractor problem. What would happen then? Perhaps the .40 would be shoved too far into the chamber to be ignited by the firing pin. Or perhaps the firing pin would ignite the .40 while its only partially into the chamber, but further away from the bolt face than normal. The former may not be so bad, but the latter may cause a safety situation with the .40 brass actually being able to jump backwards toward the bolt face after ignition.

Another thought is this: If the .40 round does ignite beyond the extractor, the case will move backwards to the bolt face before the brass expands. Moving bacwards takes less energy than the expansion of the brass. That means there can be gas leakage around the mouth of the brass before it expands to seal the chamber.

You know, it doesn't sound like such a good idea anymore.


Just a thought.