NRA Article Says 308 Ammo's Unsafe in 7.62 Chambers

Interesting all the stuff that goes on at the fringes.

Were those M14 NM "service rifles" being shot with .308 chambered the same as a standard infantry rifle? GI minimum? A specific military match reamer? Commercial?
 
Jim Watson said:
Interesting all the stuff that goes on at the fringes.

Were those M14 NM "service rifles" being shot with .308 chambered the same as a standard infantry rifle? GI minimum? A specific military match reamer? Commercial?
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Don't know for sure. Can't find M14NM chamber specs to compare with regular service rifles.

All the USN Garand 7.62 NATO barrels were made to M14 service specs. The ones from Springfield Armory were air gauged for groove diameters and those in the .3077" to .3079" range were set aside for match conditioned Garands. These were put in good receivers then paired with a bolt that just closed on a 1.630" GO headspace gauge.

Best accuracy in both service rifles was with commercial match ammo. Test groups were a third the size of M118 or M852 from Lake City ammo plant
 
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the headspacing on most 7.62 NATO chambers will run 0.006 to 0.010 inch longer than their sporting rifle counterparts,
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I wonder just where that comes from, the author doesn't say.

and then warns us of the possibility of a ruptured case shooting .308 in the military chamber.

OK, forum members, here's a "fire mission", we've got hundred of years of experience between us, can anyone provide a documented (or personally observed) case of commercial .308 Win ammo rupturing a case due to being fired in a 7.62x51mm chamber?? (and not for some other reason)

I don't know of any.

I realize its possible but very few folks run commercial .308 through 7.62 machineguns, and I don't think rifle chambers are quite as deliberately sloppy. SO I don't think its something to be particularly worried about. Can you prove me wrong?

The thought also occurs to me, that chambers marked 7.62 NATO in semi autos, intended for the civilian market might not be cut as "generously" as ones for actual military arms.

I do agree with running 7.62 NATO in guns so marked, not because of any significant risk shooting .308Win, but because the NATO round is the one the rifles are built for. Kind of like not running commercial .30-06 in an unmodified M1 Garand. Run the gun on what it was made for and you avoid even potential problems.
 
308 WIN 1.6300" - 1.6340"/Field 1.6380"
762 NATO 1.6355" - 1.6405"

Looking at the article... is the only reason for not firing commercial in a military chamber that of thinner/lighter commercial case walls in a chamber "potentially" beyond 308 Field gauge by ~0.002" ?

Do I assume that all other case headspace dimensions/specs/tolerances are the same for both military & commercial ammunition ?

So case wall thickness is it?
 
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It's been a long time for me, but if I remember things right, if the bolt closed on the FIELD gauge, the rifle was NOT sent back to the field, it had to be repaired.

You risk case rupture (ANY AMMO) if your chamber exceeds Field gauge.
 
I always thought the field gauge was kind of a misnomer. I had assumed that the no-go was a hard stop and the field gauge was to let you know you're getting close to it, it's more like the opposite.

The No-Go lets you know you've exceeded headspace, the field gauge helps you determine whether you've bumped a little past it and it can run for a little while if need be or if you've blown past it and got a dangerous situation. Of course, I'd never shoot a gun that was past no-go if I had a choice.

Springfield M1As chambered in 7.62 NATO come with a tag warning that headspace has been set specifically for that caliber and commercial .308 should not be used.
 
Having measured case headspace on all sorts of 7.62 NATO ammo, never seen one greater than 1.630 inch. Ditto with new commercial 308 Winchester ammo.

I read years ago that new military cases can safely stretch several thousandths in their web on first firing in chambers with maximum +++ headspace. The article mentioned such cases from those extreme conditions may not be safe to reload.
 
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It would appear that the NRA article states the 7.62 Chamber can exceed 308 Field dimensions ... and still be just fine w/ military ammo.
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I read years ago that new military cases can safely stretch several thousandths in their web on first firing in chambers with maximum +++ headspace. The article mentioned such cases from those extreme conditions may not be safe to reload.
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I would remind all that the military does what the military wants to do, and generally doesn't care about civilian specs. Nor do they care a lot about their own specs, (once initially accepted) other than small numbers of special purpose guns (match rifles,etc.)

The military requires the cartridge case to survive ONE cycle. Feeding firing, extracting and ejecting without failure. That's it. Once the brass leaves the gun, it is scrap (to them) and it doesn't matter if it is safely reloadable scrap or not.

the most famous, among reloaders, example of this is the .303 British. Headspacing on the rim, .303 chambers (military arms, not sporting rifles) are usually charitably described as "generous". This is a polite way of saying oversized. It's actually desirable, from the military point of view. So long as the brass functions properly ONCE, they're fine with it.

Springfield M1As chambered in 7.62 NATO come with a tag warning that headspace has been set specifically for that caliber and commercial .308 should not be used.
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OK, TODAY they do (since you say so) but in the early days they didn't. My guess is that tag and its warning is legal CYA for Springfield, just in case...

Modern commercial ammo usually has some kind of warning with it, generally stating something like "use only in modern firearms in good conditions originally chambered for this round" or words to that effect.

If your rifle says 7.62 NATO, then its NOT a .308 Win and vice versa. Shoot anything other than what is marked on the gun, and from a liability standpoint, its like what the Preacher in Blazing Saddles said after the bible he was holding up was shot.... "Son, you're on your own..."
:D
 
If your rifle says 7.62 NATO, then its NOT a .308 Win
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More correct to say
"If your rifle says 7.62 NATO, then it MAY not be 308 Win"
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Check the headspace, since as far as anyone here apparently knows, that's about all the difference is.
If it's 1.6300" - 1.6340" then no issues.

NOT ADVISING -- But an interesting take:
- Turn the gas off.
- Fire one Round.
- Measure the case shoulder dimension.


.
 
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The DCM and CMP never (as far as I know) cautioned state shooting organizations about this conundrum issuing M14NM rifles to them knowing commercial 308 Winchester ammo would be shot in them. Especially as military teams shot the same commercial ammo that would be shot in them.

All this clashed with what service personnel issuing military 30-06 and 7.62 match ammo to folks shooting EIC leg matches at the Nationals to not shoot that stuff in commercial rifles. Then military teams would shoot handloads or commercial match ammo in the NRA service rifle divisions events using M14NM, M1A or M1 rifles

Shooting 7.62 proof loads whose cases were minimum dimensions producing 82,000 psi average never had problems when fired in maximum dimension chambers
 
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44 AMP said:
If your rifle says 7.62 NATO, then its NOT a .308 Win and vice versa. Shoot anything other than what is marked on the gun, and from a liability standpoint, its like what the Preacher in Blazing Saddles said after the bible he was holding up was shot.... "Son, you're on your own..."
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So, it's not safe to shoot ammo marked 30-06 in Garands marked "CAL 30 M1?"

Cans and boxes of ammo for military rifles and machine guns were labeled both ways.
 
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I find this amusing considering CIP does not differentiate between 308 & 7.62 X 51 nor do they differentiate between 223 & 5.56X45.
 
"If your rifle says 7.62 NATO, then its NOT a .308 Win and vice versa. Shoot anything other than what is marked on the gun, and from a liability standpoint, its like what the Preacher in Blazing Saddles said after the bible he was holding up was shot.... "Son, you're on your own..."

OK, so how do you explain that fact that there are ammo manufacturers' boxes that use .308 and 7.62x51 interchangeably, on the same box? I currently only have milsurp .308 on hand or I would show some boxes. Anyone have some they can post?
 
So, it's not safe to shoot ammo marked 30-06 in Garands marked "CAL 30 M1?"
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I did not say that. What I said was, if you shoot something other than what is marked on the gun, from a liability standpoint, you're on your own.

OK, so how do you explain that fact that there are ammo manufacturers' boxes that use .308 and 7.62x51 interchangeably, on the same box?
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Other than the obvious, "because they can" I have no idea. Personally haven't seen any marked with both labels. Why do you expect me to explain what someone else does?


Personally, I think the whole thing is a tempest in a teapot. Possible, I suppose, but people have been shooting commercial .308 ammo in military firearms for almost 70 years now, and there hasn't been any significant number of problems reported during that time, so, I suspect the future won't be much different.
 
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