Shooting .40 in a 10mm (That's not a Glock)

A Glock 29 is now on my wish list as a versatile ammo hog. My Glock 22 has a .22 kit, 9mm and .357 sig conversion barrels to go along with its .40 caliber. I want to do the same to a 10mm now.
 
Hammerhead said:
I have a book on the 1911 that shows two blown 40 cases fired from a 10mm 1911.
The case gets ahead of the extractor, and the long firing pin on a 1911 is able to reach it.
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That didn’t sound quite right. So I had to go check for myself.

Using a Colt Delta Elite, I see the firing pin could indeed contact the primer of a .40 that was out in front of the extractor and seated at the end of the chamber. However, being seated more deeply in the chamber, the case would be fully supported at the moment of firing. Much more so than any 10mm or .40 that was chambered with the case head up against the breech face. This is actually an example of a fully supported case. See below.

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For comparison, here is what a 10mm looks like when chambered correctly. Notice the unsupported area in front of the extractor groove. This is normal.

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Now what would happen if one fired the deep-seated .40, without the mass of the slide directly behind it, the case would be shoved backward, snapping the rim past the extractor until it comes in contact with the slide, and then continue cycling as normal. So true, the case would begin to move out of the chamber while the pressure was higher, but it would still be stopped at the point where the recoil cycle usually starts, and with the same amount of uspported case at this point.

I suspect the instance you read about was caused by a gun with an excessive unsupported area of the chamber. I understand 10mm brass is thicker in this area, and so the issue never manifested. When a thinner .40 case was fired in this particular chamber (with the rim either in front of or behind the extractor), the case was insufficient for the excessive chamber and it failed.

It’s a thought, anyway.

FWIW, I’ve fired a couple hundred .40s through a Colt 1911 without issue, and through a couple of Glock 10mms as well. The only “issue” I have noted was that having the case head not pressed firmly against the breech face allows for excessive primer flow. Reading the primer gives the impression of a massively overpressure cartridge. However, it is just from having insufficient support for the primer.

Having said all of that, I have guns chambered in both calibers, so I can shoot the “correct” cartridge in each gun. But should I find myself with only a 10mm and no ammo was available, I would not be uncomfortable substituting .40 for use.
 
I suspect the instance you read about was caused by a gun with an excessive unsupported area of the chamber. I understand 10mm brass is thicker in this area, and so the issue never manifested. When a thinner .40 case was fired in this particular chamber (with the rim either in front of or behind the extractor), the case was insufficient for the excessive chamber and it failed.
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That's your assumption, not mine.
I'm just passing along a warning from a reputable source, not internet speculation.
 
In the Golden Age of surplus guns, there were a lot of Spanish 9mm Largo pistols sold surplus. The story was that in particular, the Astra 400 was an "any 9mm" gun capable of being shot with 9mm P as well as its intended 9x23 Largo/Bergman Bayard round.

And it was, usually. The 9x19 would "headspace" on the extractor or on the case/chamber taper and all was well. But if a 9x19 got ahead of the extractor and the long protrusion firing pin set it off, it did not just push back "snapping under the extractor." Maj. Geo. C. Nonte was a big gunzine contributor at the time and he showed pictures of blown primers where the case expanded enough to hold in position forward with no head support.

So I think you are taking a bit of a chance shooting .40s in a 10mm DE even though you can get away with it in a Glock or other gun with limited firing pin protrusion.
 
Always best to use the ammunition required per the manufacturer, as marked on the barrel...all else is an experiment. Spend some $ on a Storm Lake bbl. in .40 S&W. Mine's been 1st rate...a 9mm conversion bbl. for a Glock 23 .40.

That said, you might check out Ken Water's evaluation of a Colt Delta Elite in 10mm in one of his "Pet Loads" articles. In it he tries .40 S&W with some interesting results. Best Regards, Rod
 
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