Is it safe to headspace on bullet instead of case mouth?

[shawnba67]

I'm going to second some rep!

 

[Bosshoss]

Shawn just to add to the discussion FWIW.
I know several shooters over the years that shot SHORT ammo in their guns. 9X21 used to be popular in USPSA and I knew several shooters that shot 9X19 thru the same guns when shooting steel matchs- no need for major loads for steel. I used to stock reduced power recoil springs(still have some actually) for glocks 10 mm because several shooters shot .40 S&W out of the 10 MM glocks. I have fired 9MM out of my .38 super race gun before. It required a differant extractor and recoil spring but it did work. I heard a couple of shooters that didn't reload say they bought and used .45 GAP because that is all they could find this spring and they shot it out of their .45 ACP glock and 1911.
I wouldn't mess with unknown pressures making long bullets but I wouldn't hesitate to try standard length .40 out of a 10mm gun with a recoil spring change. I don't know if it will run reliable or not but if it has a good extractor and you get the recoil spring right it might run.
Some guns magazines are pickey about OAL and it might cause feeding issues but you won't know until you try.

 

[rvb]

I am just challenging the common believe of case mouth headspacing. Having been told something your entire life doesn't make it true, only beleived.

It is by DEFINITION headspace is off the case mouth on most semi-auto pistol cartrdges, not "common belief". Just like headspace is off the cartridge shoulder on most bottleneck rifle chambers and off the rim of rimfire or rimmed center fire ammo. Headspace is a min and max dimension that allows a cartridge that is w/in the proper dimensions/tollerances to fit w/in the chamber, get hit by the FP, and not stretch the brass to the point of failure (especially important in rifles). A cartridge should always have some looseness in a chamber; headspace doesn't mean wedged.

There are times headspace isn't off the expected points, but those are the exceptions. For instance, .38 super was intended to be headspaced off it's rim, iirc. Most gun builders today leave lots of clearance around the rim, and instead headspace off the case mouth. So there's some "tribal knowledge" there, but it's for a practical reason (eg the .38 super variants that are rimless).

You can buy headspace gauges for every caliber... they do not look like a cartridge w/ a bullet. You can get tools to exactly measure headspace (off the appropriate point) so you can size/trim your brass accordingly, or go/no-go gauges that make sure your chamber is 1) big enough a max dimensioned case will fit and 2) small enough a min dimensioned case won't fail/rupture. W/ pistol pressures, you typically don't have to worry about the latter.

http://www.brownells.com/gunsmith-t...ace-gauges/go-no-go-gauge-sets-prod26876.aspx

In a perfect world, where case OAL never varies by more than 1 or 2 thousandths, he's actually correct. However, in the real world bullets are not so uniform and neither is neck tension. All it would take is for one work-hardened piece of brass to have very little neck tension, such that when the firing pin strikes the primer, the bullet sets back into the case 5-10 thousandths. Now, you not only have a case with excessive headspace, but increased pressure during the firing sequence; a perfect storm for a headcase separation.

That's the exact concern I was alluding to in my earlier post.

It's not just the pressure/safety issue.... Again, if you are planning to have the bullet touching the rifling, or w/in a couple thousandths, expect reliability problems. I had some long loaded 147 9mms that ran fine in one gun, but in another about every 1 in 50 would cause failures to go completely into battery as they sometimes hit the rifling too soon (same batch of bullets, same progressive press, quality Zero fmj, etc). Had to beat it out vs a simple racking as they wedged in pretty good. Ogives are not 100% uniform, so even if your oal is w/in 0.000001" (impossible) you might be varying the distance to the rifling a couple thousandths.

Whatever gun you're shooting, just get a .40 barrel fit. It'll only cost you a couple hundred bucks, which will pay foritself by not buying 10mm brass.

-rvb

 

[CountryBoy19]

It is not safe to fire a cartridge in a chamber marked and designed for another cartridge.

If the shooter next to you, the RO behind you, or you, get hurt you are totally on your own. Legally and morally. It could even be criminal.

Fer petes sake, don't bring your contraption to any match I am at.

I won't discuss the technical aspects of what you are attempting. There are rules that need to be followed. One of the gun rules is to only shoot cartridges out of firearms that are chambered for that cartridge.

Oh, you mean like don't ever shoot .223 in a 5.56 or 38 Spl in a .357 mag or .22 short in a .22 long or long-rifle?

Or maybe, you just drew some conclusions about how dangerous this sounds before thinking about it first? There are many instances where guns shoot cartridges that they aren't necessarily chambered/marked for. It's a case-by-case basis and all aspects must be taken into consideration before doing so. The OP has come here to bring those aspects into discussion and that's what we're doing.

Sorry bud, gotta disagree w/ you on this one. Loading into the lands is NOT the same thing as HEADSPACING. when loading to the lands you are still putting the proper size brass into the proper size chamber allowing proper expansion and sealing. Putting a casing into a chamber that is not headspaced for it is a recipe for disaster.

You can load into the lands, but the casing must still be headspaced properly to the chamber.

Based upon your later responses I think we're on the same page now. Not necessarily advisable but not as dangerous as some are making it out to be...

 

[sloughfoot]

Oh, you mean like don't ever shoot .223 in a 5.56 or 38 Spl in a .357 mag or .22 short in a .22 long or long-rifle?

All of your examples are endorsed by the firearms manufacturers. They were tested and proven to be safe. I don't think we can say the same thing about the dangerous practice that the OP opined about doing in his original post, (but has yet to try) of jamming the bullet into the lands. Anybody who tries this unproven, untested, un-endorsed procedure is truly, totally on their own, legally and morally.

Some things should not be tried. Or at least not talked about on a public forum. And that can be used against someone later if someone gets hurt. Especially if someone reads all of this and decides to try it for themselves. These words will not go away after we stop talking about this. They will always be out there......

I believe it to be a dangerous practice to try this. Nothing will alter that opinion. I believe it far better for the OP to install a 40 S&W barrel and take what that cartridge will give him.

Making major is nice and can help, but even shooting minor is still a clean if you just keep them in the A-zone. And I think this is all about shooting in matches, not end of the world survival with whatever you can scrounge and make work to survive.

Heck, even the US Army has a list of cartridges that will "work" in various calibers of military weapons if that is all you can get a hold of....But that is for the extreme condition and as a last resort. Not for a silly pistol match at your local gun club next Saturday at 9AM.

 

[SSGSAD]

Here you go




Having your case to short, or you chamber to long is an unsafe condition.


Lets also add to the picture on the right, that it also leaves the case unsupported which is also dangerous w/ higher pressure loads.

I am going to say, that if there were no "space" at the end of the "shell", what about the case stretching?????
JMHO, but this is also why, you "have" to trim, semi auto, and you do not "have" to trim revolver cases..... ie, .38 spl., in a .357 Mag. chamber .....

 

[Broom_jm]

I am going to say, that if there were no "space" at the end of the "shell", what about the case stretching?????
JMHO, but this is also why, you "have" to trim, semi auto, and you do not "have" to trim revolver cases..... ie, .38 spl., in a .357 Mag. chamber .....

If the firing and resizing of semi-auto cases actually resulted in case stretching, your question would have a good deal of merit. However, most folks have noted that their semi-auto brass does not stretch; if anything, it is almost always shorter than the trim-to length. I explained why in a previous post. Most of the time SA cases are set back, flush against the breech when the firing sequence occurs. Contrary to some misconceptions, bottle-necked brass does not typically grow in length during the shot, but during the resizing process. Most pistol brass just doesn't grow in length, for the most part.

Try this experiment: Measure 5 pieces of 30 carbine brass before firing. Measure those same cases after they've been fired. Resize the cases and measure a third time. You'll find that they start out around 1.288", get shorter when fired, and are stretched out a little during resizing. The same is typical of pistol brass, although it is unlikely to ever exceed trim-to length, whereas 30 Carbine brass frequently does.

 

[bigerik]

It was meant to Head space on the case mouth. That's were id stay (playing with things that explode close to your face need to be correct or it could end up in your face. Load to spec and stay within safe presures. You and ur firearm both will be much healthier for it. Want more power buy a bigger gun..
As a gunsmith/reloader that's my advise.