# PSA: don't shoot .308 ammo in a 7.62x51 chamber



## Ready.Fire.Aim (Sep 22, 2009)

Great article with photos. 
http://www.mssblog.com/2016/09/16/7-62x51-vs-308-win/

I excerpted the following

Comparing .308 Winchester and 7.62X51: The difference in these two is the headspace. NATO is ridiculously longer.

Although there are different pressure-testing standards used by NATO and SAAMI, .308 commercial is normally loaded to a higher pressure maximum than mil-spec NATO.

Itâ€™s safe to shoot NATO rounds in a .308 Win. chamber. The difference comes in shooting a commercial .308 in a NATO chamber. At the least, the commercial case will be stressed, a whopping lot. Numbers?

SAAMI-spec headspace for a .308 Win. is a minimum (shortest allowable headspace or â€œGOâ€ figure) of 1.630 inches, and a â€œrejectâ€ (too long) figure of 1.634. Well, the number given as a minimum for NATO is 1.638. 
The â€œrejectâ€ on NATO is 1.6455.

Iâ€™m not at all clear on why anyone thought that was a good idea, but thatâ€™s what was done. It is also the reason that NATO cartridge case specs call for considerably thicker-walled brass.

It has to endure that much more expansion. Itâ€™s a big reason not to purchase â€œsurplusâ€ 7.62 brass for reloading. Well thatâ€™s my adviceâ€¦ Cases fired through a true NATO chamber will be patently worthless to anyone owning a .308 Win. Theyâ€™ll be blown beyond all reasonable repair.

Have fun
RFA


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## peckerwood (Jun 9, 2012)

Good info! I've shot lots of surplus stuff in my Husqvarna with no problems at all,but never thought of the other way around.Thanks for the post.


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## Chase4556 (Aug 26, 2008)

All we load for our 308s is military 7.62x51 brass. Never the slightest issue. Once resized and trimmed, they fit right into my wilson case guage as well. Loaded to 308win specs. 

Not saying I'd fire commercial 308 through a 7.62x51. I have always heard they are opposite of 5.56 vs 223, and that its more dangerous of a swap than 223 and 5.56.


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## muney pit (Mar 24, 2014)

Unless your shooting a beltfeed or older m1a rifles its a non issue. Still, its good to know. Its like owning a Porsche. Most dont know it cost around $300 to get the oil changed, but the people who own one do. If you have a rifle that is chambered in 7,62x51 im betting you know it.


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## Ernest (May 21, 2004)

Running good .308 ammo in a decent 7.62X51 weapon is no problem. It merely leads to a slight decrease in brass life due to the case stretching. 

Some 7.62x51 may be a tight fit or too long for .308. But, if the bolt closes, no problem firing it. 

Moreover 7/1000's of case growth upon firing is not considered excessive expansion, not does it necessitate thicker walled brass. Commercial .308 grows/head space lengthens something like 7 or 8/1000 in many .308 chambers. 

But, be it .308 or 7.62x51, if you have the case grow 7/1000 with each firing (bumping back shoulder each time to min. length), then you will see decreased case life.


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## Ernest (May 21, 2004)

Moreover 7/1000's of case growth upon firing is not considered excessive expansion, nor does it necessitate thicker walled brass.

Sorry typo.


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## texastkikker (Dec 24, 2008)

hummmmm.....never thought about this......so I have a Larue PredatAR 7.62 and I shoot Hornady .308 168 gr BTHP through it......am I OK?


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