Shooting 40 S&W in a 10mm Semi Auto?

[Sig556r]

What he said. Next we'll have some fools shooting 308s in a 30-06 !

I inadvertently did, fireformed the 308 case till it ran out up to -06 shoulder.
Also fired a 380 on a 9, did eject but FTF.

[Lloyd Smale]

but how could it possibly headspace??

Just for the sake of argument, it can be done.

[Peregrine]

What he said. Next we'll have some fools shooting 308s in a 30-06 !

I heard from a guy who worked at a gun store that once he had a gentleman walk up to him and ask where the 30-06 shorts where. Turned out the guy had been buying .308 for years and shooting it through his .30-06 but that one day couldn't find it because the packaging for his brand had changed slightly.

Also read about (I think here) an anecdotal case where a BAR was among several weapons being used for familiarization and fed several magazines worth of .308.
Functioned flawlessly until someone wised up.

[Petrol & Powder]

Lloyd, we all agree that a rimless casing CAN headspace on the extractor. You seem to be the only one that thinks semi-auto pistols are DESIGNED to headspace the casing on the extractor.

[35remington]

And it should come as no surprise that when correct ammo is used in in chambers intended for it in autoloading pistols, the ammo does not headspace on the extractor.

To proclaim that it does as a common event is contrary to what is actually occurring.

[DougGuy]

Here is an interesting pair of barrels, sent by a member here that I think has posted in this thread already about using 40 brass and seating to 10mm COA. This job was to throat a 10mm barrel so it had freebore enough to handle anything that would cycle through the magazine, and throat the 40 barrel with enough freebore to feed and fire ammo loaded to 10mm COA dimensions.

10mm barrel on the left, long throated 40 S&W barrel on the right.



Dummies sent in request to cut the throat deep enough to plunk these.

[35remington]

And before the above post gets misconstrued.....the rounds so loaded are not headspacing on the extractor either, as DG just cut a deeper throat. He did not move the location of the chamber shoulder in the 40 barrel.

[Lloyd Smale]

nope never once said they were intentionaly designed to headspace on an extractor. But if you trim your brass, over crimp and even many guns with a bit long chamber rim then theory goes right out the door. If your gun is cut to headspace trimmed brass then not keeping it trimmed exactly to fit your gun is going to cause jams and if your gun is cut to handle longer cases (which most are) then a short case is going to headspace on the extractor. Belted mag rifle cases are designed to headspace on the belt too but how many handloaders actually do it?

So yes if you do trim your brass to fit each individual gun you have in that caliber to the exact length to bump the rim in your chamber you can say your headspacing on the rim IF your not over crimping. Me? Ive used mixed brass from many manufactures and have multiple 9s 40s 45s 10s and haven't trimmed a piece of handgun brass in 30 years. Never saw a piece of brass even fired 10 times not pass a plunk test. So obviously the shoulder in the chamber on most guns allows for some room and if so sure isn't headspacing a thing. Now ive seen guns that weren't cut like that. My neighbor who passed a few years ago bought two new springfield xd's many years ago when they first came out. Both were 45s and we took them to the range the day he got them and I grabbed a couple different loads I had loaded in coffee cans. Neither of those guns would run that ammo. We found for those two guns to work reliably brass had to be trimmed at least to minimum spec. Ive owned a few later xds and never had that problem so my guess is some of the early ones came out like that and it caused enough people to complain about reliability that they used a different reamer.

Just go and buy 5 different brands of 45 ammo and pull a bullet and measure each case and youll see variations in length. So unless theres some magic going on and the manufacture made a automatic adjusting shoulder in his chamber not all that ammo is going to headspace on the shoulder. Manufactures (at least ones that want reliability) have to cut chambers on the generous size to account for this and to account for the fact a gun gets dirty. Heck ive even came home after shooting a few hundred rounds through a gun with no trouble and when cleaning it found a ring of lead right at the shoulder in the chamber and the gun still went bang every time. IF the case was headspacing right on the shoulder it then would be headspacing on that ring of lead and it surely would cause problems immediately.

Heck ive shot a couple thousand rounds through my glocks without a cleaning and with lubed cast bullets and had them coated with gunk on in the chamber and they like the energizer bunny keep running an running and do it with any brass I find at the range. Maybe they do have a self adjusting shoulder I don't know about. So are they designed to run headspace on the shoulder? Nope that's not what the college grad ballistics experts who sit and design a new gun will say. But I don't put to much store in theory. In the real world the only time I worry about a semi auto handgun round being properly headspaced on the rim is in a ruger single action that has no extractor or moon clip to do that duty. Its why I don't have any convertible rugers anymore. I don't have the time or patients to trim brass and keep separate ammo for them. If I cant grab a coffee can of mixed brass ammo and go blasting and go blasting reliably its not worth my bother to own. Me? if I had to trim every piece of handgun brass even once id have wore out many power trimmers. Heck ive wore out a couple just doing 556 brass. Ive said my piece and am out of here. Ive got to cast some soft bullets so they can bump up in my guns today too. Because some expert told me it was nessisary

Lloyd, we all agree that a rimless casing CAN headspace on the extractor. You seem to be the only one that thinks semi-auto pistols are DESIGNED to headspace the casing on the extractor.

[Forrest r]

Slides and extractors are cheap enough. The primer will take longer to seal in the 40s&w case and the pitting ring from the hot gasses will happen faster/pre-mature. This is common with the use of srp in 9mm/40s&w and low power factor loads. Extractor replacement is easy enough/cheap enough.

I wouldn't shoot 40s&w's in a 10mm myself, bbl's are cheap enough.

Head spacing on the case mouth:
It's right up there with crimp/too much crimp. Anyone can do a simple test. Buy four different boxes of factory ammo & shoot 1/2 of each box with the extractor in the pistol. Note any ftf's and keep that brass separate to compare fp hits later on. Remove the extractor and re-test using the other 1/2 of each box of ammo. Note any ftf's and compare the fp hits to the brass that was fired with the extractor installed.


If the extractor is meaningless to a chambered round being fired:
There should be no ftf's (failure to fire) with or without the extractor installed.
The fp hits should have the same depth in the primers.
The fp hits should be centered.

[Petrol & Powder]

Lloyd, you didn't say they (the guns) were designed to headspace on the extractor but you sure did imply that the extractor is more important to headspacing than the cut at the front of the chamber.

From post #24, "..........Realisticaly all semi autos headspace on the extractor"

[Petrol & Powder]

And you implied it again in post #29, ".............Santa or God doesn't hold that cartridge in the proper spot to insure your gun goes bang your extractor does."

[Petrol & Powder]

And you really hammered your view point home at the end of post #24:

Lloyd wrote : "yup that's the real problem with doing it over the long haul. Ive done it in my 22 glock and it worked fine. But plan on using a wire brush on your chamber every time you do it and even then if your talking 10k rounds your going to probably end up with a rough chamber. As to extractor were or headspacing ill say this. Realisticaly all semi autos headspace on the extractor. If you loaded 10mm so that it actually head spaced on the rim it wouldn't take many rounds to gum the gun up and reduce reliability. Youd also have to trim brass regularly and I can honestly say I haven't trimmed handgun brass in 30 years. My guess is 99.9 percent of the ammo that goes through semi autos doesn't have the rim touching a thing. "

So yes, I agree that you never explicitly stated that you believe the guns are designed to headspace on the extractor but you sure did make your opinion on the importance of the extractor a key point in the expression of your views.

[Elkins45]

Here is an interesting pair of barrels, sent by a member here that I think has posted in this thread already about using 40 brass and seating to 10mm COA. This job was to throat a 10mm barrel so it had freebore enough to handle anything that would cycle through the magazine, and throat the 40 barrel with enough freebore to feed and fire ammo loaded to 10mm COA dimensions.

10mm barrel on the left, long throated 40 S&W barrel on the right.



Dummies sent in request to cut the throat deep enough to plunk these.

Yep, that person is me. The bullet shown seated in the dummy rounds is the NOE 200 grain WFP. FYI the "40 long" gets loaded using the low-end recommendation for 10mm and has functioned flawlessly so far. DougGuy did a fantastic job throating the barrels BTW. I wouldn't hesitate to recommend him if this is service you need.

[35remington]

Lloyd, you also stated you never trimmed a handgun case in all your years of reloading. Post 24. Which means your cases as you use them are headspacing on the case mouth because you did not deliberately trim any super short.

You spent a great amount of text explaining in favor of something that is not occurring.

Do yourself a favor and do some measuring before arguing a point. The first thing to note is how far the extractor lets the case get from the breechface. Once that is noted, the fallacy of extractor headspacing is very evident. This saves laboriously typing out an erroneous response.

If you had done some measuring you would also know your contention that chambers are cut so sloppy that they allow the extractor to headspace is also not the case. Information trumps verbosity.

If your friend’s xd’s were not accepting cases, they had an undercut short chamber. These definitely were not headspacing on the extractor. Your arguments are contradicting themselves yet you do not recognize that they are.

What I am saying is not in the realm of theory. It comes from measuring actual guns and chambers and the fit of ammo in those guns. Since you have not done any measuring, the theoretical argument is the one you are making. Time to start measuring.

[Sig556r]

I've never trimmed pistol brass either, even .357sig (factory or .40SW converts), but I agree with SAAMI & Sig that the round headspaces on the case mouth & not on shoulder, much less, on the extractor.

[cwlongshot]

Wow..

A entire 3 page thread about nothing that really matters...and some strong opinions as if convincing another person on a forum was enough to require three pages to do so.

No dog in this convo as my opinion, like all, means nada. Because things work or don't work and the world spins regardless of what any of us "think".

I for one think its run its course.

CW

[35remington]

The troubling part is suggesting that this all can be resolved if some measuring was done, yet that person is absolutely determined not to measure anything. Opinion is a poor substitute for knowledge. It is possible to really not want to know how things work.

I will suggest my opinion means more than nada as I’ve made the attempt to resolve the issue with data from actual examples over multiple makes of guns.

[Elkins45]

I've never trimmed pistol brass either, even .357sig (factory or .40SW converts), but I agree with SAAMI & Sig that the round headspaces on the case mouth & not on shoulder, much less, on the extractor.

SAAMI and the reloading manuals all say it headspace on the mouth, but apparently the people who chamber barrels do not agree. You will note that the headspace gauge pictured below does not have a case mouth. My experience in loading for the round since the mid-90's is that the barrel makers headspace it off the shoulder, and I actually had to grind the bottom off my RCBS sizing die so it would set the shoulder back far enough for my reloads to chamber in more than one 357 barrel.

[Lloyd Smale]

because in truth it is.

Lloyd, you didn't say they (the guns) were designed to headspace on the extractor but you sure did imply that the extractor is more important to headspacing than the cut at the front of the chamber.

From post #24, "..........Realisticaly all semi autos headspace on the extractor"

[Lloyd Smale]

which it does

And you implied it again in post #29, ".............Santa or God doesn't hold that cartridge in the proper spot to insure your gun goes bang your extractor does."