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40 S&W in a Glock 10mm.

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#3 ·
Conversion barrels in a G20 work just fine, and are very safe. But shooting .40 out of a 10MM barrel is a bad idea, and while you can usually get away with it, it's not considered safe by those who actually know something about guns & how they work. That's why conversion barrels are made.

However, it's a certainty that a few people are going to jump in here and tell you to go ahead and shoot .40 out of it and skip buying a .40 caliber barrel. That would be like riding a motorcycle without a helmet just because some moron said he did it a few times & didn't wreck. Don't listen to it. Buy a conversion barrel.
 
#4 ·
Buried in the last thread Brian but still haven't learned. Keep spewing that legal garbage. Tell us Brian, what exactly is going to happen that's going to cause a catastrophic failure when you shoot a .40 out of 10mm barrel? And let's get specific here, not, "It's a bad idea but I can't explain why ... I just know that it is because my grandaddy said so."
 
#6 · (Edited)
I have a stock length lwd .40cal conversion barrel for my g20sf, and I cant say a bad thing about it, it works great. If it came down to it, I would use it for carry purposes.

And before you ask...yes, ALL you need is the barrel, the stock mags and everything else will work fine!
 
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#7 ·
BillyNg said:
Buried in the last thread Brian but still haven't learned. Keep spewing that legal garbage. Tell us Brian, what exactly is going to happen that's going to cause a catastrophic failure when you shoot a .40 out of 10mm barrel? And let's get specific here, not, "It's a bad idea but I can't explain why ... I just know that it is because my grandaddy said so."
Click to expand...
Brian Lee is the one the OP should listen to not this gentleman and his opinion. I too own a Glock 20 and shoot only what is stamped on the barrel.While there may be no reported incidents of injury yet just because the .40 fires does not make this a good idea.There are alot of folks who come here for advice/help and telling them that this stuff is o.k. is irresponsible.
 
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#9 ·
I have fired .40 in a G20. After I was done I made sure the barrel was cleaned well before I fired any 10mm.
My only concern was that bullet material might be shaved by the chamber edge and cause a buildup that would prevent the 10 from headspacing properly. I don't know whether my concern was valid, eventually I bought a 10/40 conversion barrel.
 
#10 · (Edited)
I do not see a problem. Someone explain it to me.

Sure, the 40S&W has to "jump" a fraction of an inch to get to the rifling, but how is that any different than shooting a 38 Special out of a 357 Magnum? Revolvers are even more of a jump, even if they are the correct caliber...

ETA:

OK I see what nraman says, so you do need to make sure no shavings build -up.
 
#11 ·
It is not ideal because the only thing holding the case to the breech is the extractor. Otherwise the case would sit too far inside the chamber and the firing pin wouldn't hit it. Now, I don't particularly know if there is a big problem with it, other than the greater potential for a malfunction and double feed if you just try to tap/rack/bang through it. I suppose it is possible that with the bullet having to jump that couple mm from the case mouth to the throat, past the sharp edge of the headspace ring in the chamber, it is possible the bullet could start shaving jackets or get lodged sideways?

Actually, I just thought of it:
The risk is from shooting a lot of .40 and then trying to go straight to 10mm. The gap at the front of the chamber when shootin .40 could fill with lead / copper / fowling, forming a "ring" in the chamber. Then when you try to chamber a 10mm, the case doesn't go all the way into the chamber, and you can potentially fire with the slide slightly out of battery. That could indeed cause a kaboom.

But, with careful cleaning it may not be an issue.

I probably still wouldn't personally bother, at least not for consistent use and ESPECIALLY not for any serious purpose beyond casual range shooting.
 
#12 ·
RenegadeGlocker said:
I do not see a problem. Someone explain it to me.

Sure, the 40S&W has to "jump" a fraction of an inch to get to the rifling, but how is that any different than shooting a 38 Special out of a 357 Magnum? Revolvers are even more of a jump, even if they are the correct caliber...

ETA:

OK I see what nraman says, so you do need to make sure no shavings build -up.
Click to expand...
I really do hope that you are joking.

The only thing that is holding a 40S&W cartridge against the breach face when placed in a 10mm chamber is the extractor. Then you smack it with a firing pin.
 
#13 ·
Lindenwood said:
It is not ideal because the only thing holding the case to the breech is the extractor. Otherwise the case would sit too far inside the chamber and the firing pin wouldn't hit it.
Click to expand...
Interesting. I have not shot it. So you are saying if I drop a 40S&W round into a 10mm BBL it will just slide forward up to the rifling?

I will have to try it to see.
 
#16 ·
RenegadeGlocker said:
I do not see a problem. Someone explain it to me.

Sure, the 40S&W has to "jump" a fraction of an inch to get to the rifling, but how is that any different than shooting a 38 Special out of a 357 Magnum? Revolvers are even more of a jump, even if they are the correct caliber...

ETA:

OK I see what nraman says, so you do need to make sure no shavings build -up.
Click to expand...
The "rule" in using .38 Special in a 357 has been to clean the cylinder after the use of .38s. I had a case that I could not even chamber 357s after I used .38 because of the debris in the cylinder. I had to give it a good cleaning first.
 
#18 · (Edited)
When shooting 40s&w in a 10mm barrel, two items can contribute to possible problems:

1) Headspace is controlled by the extractor, not the chamber dimensions. There is a little fore-aft play against the breech face allowed by the extractor; this can be demonstated by working a casing against the extractor in a field-stripped slide. The casing may NOT be held tightly against the breech face because of this. Poorly supported casings are always a possible source of trouble.

2) The external contour of a 40 casing is NOT identical to the 10mm external case contour. The case length is not the ONLY difference between the two. That contour difference in the case taper can also create a poorly supported casing.

As someone else posted, you can probably GET AWAY WITH shooting 40 in a 10mm barrel, but it is NOT ideal.
 
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