# M1A Ammo in an AR-10



## fishin geezer (Jul 20, 2004)

I have an Armalite AR-10 rifle. A friend recently gave me a box of Federal (American Eagle) 7.62X51mm ammo. I fired several rounds in my AR-10 and they seemed to load and shoot okay. But then I saw a label on the box, saying that they are "For M1A Use". Does that mean I shouldn't be using them in my AR?

Pardon my ignorance of the difference between .308 ammo and 7.62.

Please enlighten me.


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## mustangeric (May 22, 2010)

Im pretty sure it just the nato round similar to the 5.56 and the .223

Sent from my SGH-T999 using Tapatalk 2


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## Pocketfisherman (May 30, 2005)

There is a difference in the chamber specifications. The Nato chamber has a longer leade that will let it fire heavier bullets which are longer. The leade is the part of the chamber where it transitions from the neck diameter into the rifling lands. Shoot that NATO type of ammo in a regular 308 chamber and you risk putting the bullet right of on the rifling lands and generating some very high pressures when it ignites. The Armalite is chambered for 7.62 NATO and can handle this ammo just fine. But don't use it in a rifle with a 308 Winchester chamber which you'll typically find in a bolt rifle.

Same rule applies to 223 and 5.56 Nato. The NATO chambers can shoot either ammo. But don't shoot the NATO ammo in the non NATO chambers that have a shorter chamber leade


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## mrau (Mar 17, 2010)

mustangeric said:


> Im pretty sure it just the nato round similar to the 5.56 and the .223
> 
> Sent from my SGH-T999 using Tapatalk 2


That's it. AR10 is .308/7.62X51 NATO. Don't try and use 7.62X39 Russian rounds. Those are for the AK's.

Edit: What pocket said. I think an example of a gun that's good for .308 but not for the NATO rounds is the REM 25?


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## fishin geezer (Jul 20, 2004)

*Thanks, Guys*

Thanks for the info. So I'm okay. I'll shoot it in my AR-10, but not in a .308 hunting rifle.


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## Bird (May 10, 2005)

Military cases (7.62 NATO) are generally thicker than commercial .308 rounds. This reduces volume inside the case and consequently slightly less case pressure. If reloading military brass to .308 load specs, its best to keep your load a 1 or 2 grains light so you don't over pressure the cartridge (per Lyman reloading manual). 7.62x51 NATO military ball ammo is loaded to lower pressures than standard .308 rounds for durability sake both with the brass and the semi auto/full auto actions. That being said, I've not had any issues shooting either 7.62 NATO or .308 Remington in any of our rifles chambered in it.

BTW-A bolt gun will have a stronger action than a semi auto. Shoot all you want in your bolt gun.


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## Ernest (May 21, 2004)

Commercial .308 chambers will easily handle the lower pressure Nato rounds. Further, Nato spec is 2.275 COAL. This is shorter than the SAAMI spec for a .308 winchester chamber, which is 2.810 max. 

The issue with the M1A is the pressure curve necessary to run the action without bending op rods. So the "For use in M1A's" indicates that the round uses a loading which can be used in an M1A without damage to the weapon.


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## THE JAMMER (Aug 1, 2005)

Ernest said:


> Commercial .308 chambers will easily handle the lower pressure Nato rounds. Further, Nato spec is 2.275 COAL. This is shorter than the SAAMI spec for a .308 winchester chamber, which is 2.810 max.
> 
> The issue with the M1A is the pressure curve necessary to run the action without bending op rods. So the "For use in M1A's" indicates that the round uses a loading which can be used in an M1A without damage to the weapon.


Listen to Earnest. He knows of which he speaks. Look in the reloading manuals and you will see different sections and different loads/powders for 308 and M1A.


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## Bird (May 10, 2005)

I just re-read your original post. Regarding your AR-10 not an M1A. That ammo your buddy gave you is fine in your AR-10. Regarding M1A's, if you want to shoot .308 Rem ammo, you'll want to get an adjustable gas block and open it a few clicks once installed. We have to do this when shooting suppressed since the suppressor back pressures the action so we bleed a little extra off to protect the action.


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## Pocketfisherman (May 30, 2005)

Bird said:


> Military cases (7.62 NATO) are generally thicker than commercial .308 rounds. This reduces volume inside the case and consequently slightly less case pressure. If reloading military brass to .308 load specs, its best to keep your load a 1 or 2 grains light so you don't over pressure the cartridge (per Lyman reloading manual). 7.62x51 NATO military ball ammo is loaded to lower pressures than standard .308 rounds for durability sake both with the brass and the semi auto/full auto actions. That being said, I've not had any issues shooting either 7.62 NATO or .308 Remington in any of our rifles chambered in it.
> 
> BTW-A bolt gun will have a stronger action than a semi auto. Shoot all you want in your bolt gun.


Did some more research, and I got it wrong and Bird above is right, but for a slightly different reason. For 308 it is just the opposite of 223/5.56 whereas it is ok to shoot Nato ammo in 308 win chambers, but not vice versa. The key reason being all 308 Nato ammo made also conforms to 308 headspace specs making the chamber leade length vs bullet length moot and the gating factor now becomes sammi pressure specs and case volume as stated above with the 308 having a higher pressure and more case volume than the nato spec. 
http://www.ar10t.com/community/grou...und-are-they-really-interchangeable?groupid=4

What I did state originally does however apply to 556/223


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## capt mullet (Nov 15, 2008)

The best info on the net on this subject can be found at m14forum.com

Definitely take a look at this thread it has more info than you need to know but you better know it before feeding your expensive rifle with just any rounds

http://m14forum.com/ammunition/100445-7-62-x-51-cartridge-vs-308-winchester-differences.html


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