Using 40 S&W cases as short 10mm loads?

[Elkins45]

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?

 

[Sevens]

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.

 

[Elkins45]

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.

 

[Sevens]

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.

 

[ZeSpectre]

I think it's been pretty much determined to be a bad idea for multiple reasons.

See this article.

 

[m&p45acp10+1]

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.

 

[ZeSpectre]

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.

 

[BruceM]

"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.



Bruce

 

[abber]

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.

 

[jmorris]

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.

 

[c.j.sikes]

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

 

[Elkins45]

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!

 

[SL1]

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.

SL1

 

[BruceM]

"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.



Bruce

 

[Don P]

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.

 

[qcpunk]

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......

 

[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.

 

[Nick_C_S]

Yeah that's a big negative vote over here.

If the gun is a Glock, get a Lone Wolf conversion barrel.

 

[NavyVet1959]

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.

 

[jmorris]

Would be fine out of a S&W 610 using moon clips and closer to your 38/357 example.