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7.62X51 vs .308 ?
#1
Someone asked me a question this morning that I couldn't answer so I thought I'd post here for opinions or maybe even some facts.

Situation:
He has a Mauser, (Chilean I believe he said), that is chambered for, (and marked), Nato 7.62X51. He said one of his friends told him not to shoot commercial .308 ammo because it 'might damage the gun, it's not rated for the higher pressure of commercial ammo'.
I thought military ammo was typically loaded to higher pressures than commercial ammo, (with the exception of 30-06 for the M1 Garand).
I know that 5.56X45 is higher pressure than .223 and I assumed the same would hold true for 7.62X51 vs .308.
Who can give me, or point me to a source where I can find the definitive answer?
I told him that I don't really know but what his friend told him sounds backwards to me. He agreed, he knows about not shooting 5.56X45 in a .223 chamber, but .223 in a 5.56X45 is safe. I told him not to take my word for it but that I'd check into it to see what I can find out.
I might even be able to get him to sign up here, let's get a good answer for him. Big Grin
TIA
There are three types of people in the world:
Those who make things happen,
Those who watch things happen,
And those who wonder what happened.
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#2
I think they have it backwards, my understanding from dealing with M1As that I use chambered for 7.62x51 has always been that 7.62x51 has slightly higher pressure than .308. I've always been told that a rifle chambered in 7.62x51 is fine for .308 as well, but a weapon designed for .308 is not supposed to use 7.62x51. I've shot both out of M1As designed for 7.62 and never had a problem with either. I think the manual that comes with the rifle says something about it too.
The forum poster formerly known as Emoticon...
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#3
Emoticon;165204 Wrote:I think they have it backwards, my understanding from dealing with M1As that I use chambered for 7.62x51 has always been that 7.62x51 has slightly higher pressure than .308. I've always been told that a rifle chambered in 7.62x51 is fine for .308 as well, but a weapon designed for .308 is not supposed to use 7.62x51. I've shot both out of M1As designed for 7.62 and never had a problem with either. I think the manual that comes with the rifle says something about it too.

Thank you.
Your understanding is the same as mine, which is in line with the guy who asked me. He doubted himself when someone told him the opposite so he started asking questions, I told him I'd try to help him find out for sure.
There are three types of people in the world:
Those who make things happen,
Those who watch things happen,
And those who wonder what happened.
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#4
mauser;165214 Wrote:
Emoticon;165204 Wrote:I think they have it backwards, my understanding from dealing with M1As that I use chambered for 7.62x51 has always been that 7.62x51 has slightly higher pressure than .308. I've always been told that a rifle chambered in 7.62x51 is fine for .308 as well, but a weapon designed for .308 is not supposed to use 7.62x51. I've shot both out of M1As designed for 7.62 and never had a problem with either. I think the manual that comes with the rifle says something about it too.

Thank you.
Your understanding is the same as mine, which is in line with the guy who asked me. He doubted himself when someone told him the opposite so he started asking questions, I told him I'd try to help him find out for sure.


I don't reload but if you have a reloading book you can prove it to him the pressures should all be listed there. I think the only phyisical difference between the two has to do with dimensions at the neck being slightly longer.
The forum poster formerly known as Emoticon...
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#5
SAAMI says it's safe.
http://www.saami.org/specifications_and_...ations.pdf
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#6
P89;165222 Wrote:SAAMI says it's safe.
http://www.saami.org/specifications_and_...ations.pdf

Thank you.
I'll check my ink cartridge and start printing 2 copies of that.
I'll keep one in my car with a copy of Pennsylvania Laws Relating to Firearms and I'll leave the other in the clubhouse at the range. There's nothing better than having printed documentation handy when someone asks a serious question and gets dubious answers.
There are three types of people in the world:
Those who make things happen,
Those who watch things happen,
And those who wonder what happened.
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#7
http://www.gunslot.com/forum/308-and-7-62x51-same-round
Quote:Is the .308 and the 7.62x51 the same round?

.308 Win vs. 7.62x51--The Straight Scoop
Before we go much further, we want to address the oft-posed question "Are the .308 Winchester and 7.62x51 NATO one and the same?" The simple answer is no. There are differences in chamber specs and maximum pressures. The SAMMI/CIP maximum pressure for the .308 Win cartridge is 62,000 psi, while the 7.62x51 max is 50,000 psi. Also, the headspace is slightly different. The .308 Win "Go Gauge" is 1.630" vs. 1.635" for the 7.62x51. The .308's "No-Go" dimension is 1.634" vs. 1.6405" for a 7.62x51 "No Go" gauge.
7.62x51mm NATO or 308 Winchester? What's the Difference?

copyright 2001 - Stephen Redgwell

Military surplus cases

Do you have a military surplus rifle chambered in 7.62 x 51mm? If so, you probably bought it to get a "308 Winchester" at a really low price. Well, you messed up. It's like looking at a rabbit and a hare. They're close, but each is distinctive, and you have to understand what you're looking at.

Early in my military career, I worked on the FNC1 rifle (7.62 NATO). For someone that had only handled civilian shotguns and rifles, this was going to be a real treat! It was only natural that curiosity would generate questions and comparisons about what I thought was the same cartridge - 308 Winchester and the 7.62x51mm NATO.[quote] http://www.303british.com/id36.html
das, proud to be a member of pa2a.org since Sep 2012.
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#8
It just seems odd...the 7.62x51 was developed right from the .308. Shrug
Although foreign manufacturing practices could very well play a part in it.
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#9
Now Im confused about this. AR magazine and other places says 308 is higher pressure than 7.62 other sources say 7.62 is higher pressure and still others say the difference is "minimal". I guess if I were in your situation I would use 308 in 308 and 7.62 in 7.62. Cant seem to find a definitive answer on this.
das, proud to be a member of pa2a.org since Sep 2012.
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#10
At this point, with the information I've seen here from different sources, I'll say that I wouldn't be as concerned about pressure differences as I would about the fact that the military chamber being slightly larger and the commercial brass being slightly thinner and not as able to stretch to fill the military chamber without splitting, cracking or some other similar failure. I might see the guy who asked me the question this weekend, I'll pass along the information I got here, (I'll have a few printed pages to give him), and I'll let him make his own decision, but I'll advise him to stick with military loads. He doesn't reload so he can't start with light loads and watch to see if his brass is showing any signs of stress or failure before going up to a higher pressure load and with commercial or military loads you get whet you get with no control over the recipe. That being the case I'm more comfortable with telling him to stick with what the chamber is identified as.
The headspace issue with firing commercial ammo in a military chamber concerns me, and that's the issue I'll make him aware of when I hand him the printed info.
Thanks to everyone who contributed here! Smile
There are three types of people in the world:
Those who make things happen,
Those who watch things happen,
And those who wonder what happened.
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