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Old August 23, 2010, 07:38 AM   #1
Elkins45
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Using 40 S&W cases as short 10mm loads?

Anybody ever use 40 S&W brass to assemble 10mm loads by seating the bullet out to get a round with full 10mm LOA? Sort of like using 38 special in a gun chambered for 357 magnum?

I would think this would be a good way to utilize some of the cheap police surplus once fired 40 brass that seems to be everywhere instead of my carefully hoarded 10mm brass. I would use it for low and moderate power loads, not full bore 10mm.

Anybody else doing this?
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Old August 23, 2010, 07:45 AM   #2
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I am not doing this -- 10mm cartridges headspace on the case mouth so shooting .40 S&W brass through semi-auto pistols chambered for 10mm is asking your extractor to do the job of holding the loaded round to the breech face. It may or may not work, but it's certainly going to stress the extractor and ask it to do something it's not designed to do.

Next up for me would be the case mouth tension of .40 S&W brass that is designed to have a bullet seated to a certain point -- I believe it would be extremely unlikely that you'd get proper mouth tension on that bullet seated out so far and that it would most likely want to or try to seat itself further in the case. If/when that happened (typically as a fresh round being violently chucked in to the chamber) you'd have a nuclear bomb as a 10mm load and a 10mm slug would now be contained in a .40 S&W piece of brass. The pressure would shoot up exponentially and you'd be begging for a catastrophic failure.

Not to mention any damage you might do to the mouth of the chamber if everything else went off without a hitch.

Yeah, .40 S&W brass is everywhere and cheap as dirt but if you want to shoot 10mm, you've got to pay to play.

*NOTE* Obviously, I'm completed against the idea but will admit clearly that I've not ever tried it in either of my 10mm pistols. My advice is nothing more than opinion with no hard evidence to back it up.
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Old August 23, 2010, 08:01 AM   #3
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Sevens, I forgot to add something that might change your thinking somewhat. I'm contemplating doing this with a cast 200gr RCBS bullet that is quite long compared to most 40 cal bullets. Given that these would be light loads there's the possibility of seating the bullet out far enough that it actually headspaces on the rifling lead.

It's something I would play with using a dummy round and the barrel out of the gun. Of course, then there's the problem that a round that long is probably too long to feed through the magazine...

What about a special cast bullet with a case diameter driving band to headspace on, sort of like a 'heeled' 22LR round? Wonder how much pressure it would take to swage that band down as it entered the chamber throat? That sound like an extraordinarily bad idea.
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Old August 23, 2010, 06:06 PM   #4
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I don't think you'd have any magazine or even feeding problems -- but unless you can seat these bullets in such a way that it's next to impossible for each and every single round to have an unintended bullet setback, I wouldn't even consider it.

Not working well or feeding poorly isn't catastrophic. But bullet setback would be.
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Old August 23, 2010, 06:16 PM   #5
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I think it's been pretty much determined to be a bad idea for multiple reasons.

See this article.
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Old August 23, 2010, 06:20 PM   #6
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Every reloading manual I have read has warned not to do that. It also says do not cut down 10mm for .40 S&W. (Why anyone would do that escapes me for logic) Just try to pick up all of your brass. The good thing is 10mm brass sticks out among all of the rest.
As a brass scrounger for over a year I have found less than 20 pieces of 10mm brass at the range. (Reason being is that the guys that shoot 10mm reload, and are methodical to not loose the brass.)
It is not worh the risk to the shooter, or the gun to save a few dollars. This is coming from a guy that is prepetualy broke, and very tight with the few dollars I get to spend for my shooting addiction.
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Old August 23, 2010, 09:09 PM   #7
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Quote:
for over a year I have found less than 20 pieces of 10mm brass at the range. (Reason being is that the guys that shoot 10mm reload, and are methodical to not loose the brass.)
You ain't just whistlin' Dixie there. I actually took some fiberglass tent poles and mesh netting and made a "catcher" specifically for my 10mm so I could relax and just shoot and still have some prayer of finding my brass.

As to the "don't cut down 10mm brass for .40, that's because the internal web in 10mm is significantly thicker and reduces case volume compared to a .40 case.
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Old August 23, 2010, 11:32 PM   #8
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"Given that these would be light loads there's the possibility of seating the bullet out far enough that it actually headspaces on the rifling lead."

Yep!

That sound like an even better idea-NOT.

You don't have capacity equal to a 10mm case when seating the bullet out because the web is different (read thicker) on a .40 S&W case.



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Old August 24, 2010, 09:58 AM   #9
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Why not just get a 40? Your plan sounds dangerous. The Sig P226 is crazy accurate in 40 cal. Once-fired brass is cheap too.
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Old August 24, 2010, 10:03 AM   #10
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Quote:
Anybody ever use 40 S&W brass to assemble 10mm loads by seating the bullet out to get a round with full 10mm LOA? Sort of like using 38 special in a gun chambered for 357 magnum?
All of the time in a S&W 610 revolver using moon clips. No go in a bottom feeder (auto) though.
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Old August 24, 2010, 03:28 PM   #11
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i shoot a wheel gun so moon clips are used. i have shot the 40 in my 10 mm and it does fine only i do not want to burnish my chamber in the 10 so i use only 10 mm brass, yes i do also have a 40 in rifle. just for what it is worth.cjs
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Old August 24, 2010, 05:34 PM   #12
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Quote:
I think it's been pretty much determined to be a bad idea for multiple reasons.

See this article.
The fact that Dean Speir is against it makes me think it must be a good idea after all!
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Old August 26, 2010, 08:47 AM   #13
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Another issue

If you use .40 S&W brass with your bullets seated-out to 10mm COL or more to make lead bullets head-space on the rifling, you may get problems with bullet mis-alignment. There is substantially more bullet above the case mouth, and that makes a greater lever-arm for the feed ramp to push the bullet out-of-alignment during the feed cycle. That would probably affect accuracy, and maybe even feeding if the bullets are pushed up far enough to grab the edge of the barrel.

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Old August 26, 2010, 05:12 PM   #14
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"The fact that Dean Speir is against it makes me think it must be a good idea after all!"

Right!

He must be in cahoots with all 10mm autoloader manufacturers or for that matter the manufacturers of any gun because they don't recommend the use in a gun of their manufacture ammo for which it is not designed or chambered for.

How ignorant of Waldo in particular and the manufacturers in general.



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Last edited by BruceM; August 26, 2010 at 05:24 PM.
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Old August 27, 2010, 08:00 AM   #15
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Quote:
I think it's been pretty much determined to be a bad idea for multiple reasons.
Good article and can't be any more explanatory as to BADDDDD Idea.
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Old August 27, 2010, 12:06 PM   #16
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Semiautos do not work like Revolvers. A "short" case for any semi auto round is not a good idea, is not safe, and will have severe reliability issues.

IMO, Don't do it!

There is a reason the two different rounds of the same caliber have completely redesigned chambers......
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Old December 10, 2014, 12:15 AM   #17
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From what I understand, the extractor on the Glock is heavy enough to do this, but that is not necessarily the case on all M1911s. I have a G29 and G20 and I regularly shoot 10mm loads using .40SW brass (at 10mm OAL). It works great.

I've also shot a lot of normal length .40SW ammo in the 10mm Glock barrel. It also works great.
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Old December 10, 2014, 12:28 AM   #18
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Yeah that's a big negative vote over here.

If the gun is a Glock, get a Lone Wolf conversion barrel.
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Old December 10, 2014, 12:40 AM   #19
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The Lone Wolf .40SW conversion barrel is only good for shooting .40SW rounds in the 10mm Glocks. It doesn't allow you to shoot .40SW brass loaded to 10mm OAL and pressure. If you ream out the chamber a bit to conform with the 10mm chamber and leave the .40SW portion of it, it would work though. There's a lot of people out there that shoot 10mm loads in .40SW brass loaded to 10mm lengths in Glock 10mm barrels. It really does work quite well.
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Old December 10, 2014, 01:03 AM   #20
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Would be fine out of a S&W 610 using moon clips and closer to your 38/357 example.
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Old December 10, 2014, 11:48 AM   #21
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Quote:
NavyVet1959
From what I understand, the extractor on the Glock is heavy enough to do this, but that is not necessarily the case on all M1911s. I have a G29 and G20 and I regularly shoot 10mm loads using .40SW brass (at 10mm OAL). It works great.

I've also shot a lot of normal length .40SW ammo in the 10mm Glock barrel. It also works great.
For years I have been reading about the extractor standing up to the firing pin force for years, but I never tried it.

I try to face my fears, but something is holding me back.

Anyway, I bought a 40sw barrel for my Glock 20 so I don't have to think about it.
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Old December 12, 2014, 09:04 PM   #22
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.40 ammo worked just fine in my stock Glock 29 (10 rounds just to experiment), but you're better off using light loads in 10mm brass or getting a conversion barrel.

People don't like to hear that their pistol may be headspacing on the extractor either, but it is often true.

Brass always seems to be on the short side of SAAMI specs, and chambers tend to run deep for reliability, so I think there's a lot of guns out there that are headspacing on the hook.
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Old December 12, 2014, 09:19 PM   #23
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Just a thought on safety, never try it in a 1911. It's possible for the .40 round to get ahead of the extractor in a 10mm 1911 chamber. The long 1911 firing pin could reach it and the back thrust could damage the extractor.

Glock firing pins have limited protrusion, so if the round gets ahead of the extractor, it shouldn't go off.

Also the KKM .40 conversion barrel does allow for longer OALs. I used 1.225" for .40 with a 165 FP and used 1.250" for the same bullet in 10mm brass.

But you don't need long OALs for feeding, standard .40 AOLs worked just fine with either barrel and stock recoil springs.

Quote:
For years I have been reading about the extractor standing up to the firing pin force for years, but I never tried it.

I try to face my fears, but something is holding me back.
That's funny. The first time I pulled the trigger on a .40 in my G-29 I really had to psych myself up to it. I flinched pretty hard on the first few.

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Old December 13, 2014, 12:02 AM   #24
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Don't own a.10. Own a .40, but no.
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Old December 13, 2014, 12:22 AM   #25
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The .460 Rowland conversion (for both Glocks and M1911s) states that you can still fire .45 ACP in it. Since the .460 Rowland brass is 1/16" longer, that means that he thinks that it is perfectly acceptable for the cartridge to be headspacing on the extractor EVEN IN THE M1911. I haven't converted a M1911 to .460 Rowland, nor do I currently have a M1911 in 10mm that I could use to test .40SW brass loaded to 10mm OAL, so I have not tested it. I'll probably end up with a M1911 in 10mm eventually, so I'll test it then. If it doesn't work, well, I've done a lot dumber things and lived to tell the tale.

Things like putting a 12 gauge shotshell in a plastic 12-gauge flare gun... Ouch...
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