Why is my rifle barrel stamped 7.62x51 instead of .308?

Discussion in 'Rifle & Shotgun Discussion' started by Chipperxd, Nov 27, 2011.

  1. Chipperxd

    Chipperxd Active Member

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    I apologize if this is a stupid question but I noticed it when I was cleaning my gun yesterday.

    The barrel is clearly marked 7.62x51 with a 1/10 twist but the receiver is marked .308.

    I know that the only real difference between a 7.62 Nato and .308 is that the .308 is a higher pressure round. I guess my questions is, is it supposed to be stamped this way? Are all DPMS rifles in .308 come with the barrel stamped with 7.62 on it?
  2. madcratebuilder

    madcratebuilder Well-Known Member

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    Myth!

    The pressure difference between a .308 and 7.62 at equal bullet weights and similar powder charge is insignificant.

    If the barrel is marked 7.62 then I would expect the chamber to be 7.62 spec. If is marked .308 then it should be .308 spec. There is a minor difference in the head spacing of the two rounds.

    You'll need to ask DPMS why they stamp their AR lowers as .308. I know that ArmaLite and Noveske stamp their AR lowers 7.62mm.

    [​IMG]
  3. Chipperxd

    Chipperxd Active Member

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    so all the forums I read where they say you shouldn't shoot .308 out of a 7.62 guns is wrong? I don't know what to believe anymore...so confused...
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  4. Chipperxd

    Chipperxd Active Member

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    Found more information online...guess the barrel is marked as 7.62 but the receiver and chamber is made to shoot both.
  5. eganx

    eganx Active Member

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    In my experience.....yes that is wrong. I have shot both out of my FAL with no problems.
  6. iamme

    iamme Well-Known Member

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    It's a battle rifle- usues mil-standard caliber aka 7.62x51.
  7. Chipperxd

    Chipperxd Active Member

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    Oh yeah, I plan on shooting the 7.62x51 NATO extensively as I just got in a crate from ammoman.com... just wanted to make sure my gun won't blow up in my face if I were to shoot some commercial .308s through it. :bluelaugh:
  8. rayd8

    rayd8 Member

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  9. Stomper

    Stomper 3%er Bronze Supporter

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    I think you got that backwards on the 7.62NATO and the .308...


    .308 fired from a 7.62NATO chambered weapon is NOT good to go... not the reverse, although my .308 Galil eats both just fine. ;)
  10. rayd8

    rayd8 Member

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    Yep, I'm corrected...thanks Stomper. I guess the other option is to check Headspace if your inclined to run 308 in your 7.62:

    Fulton Armory: What's the Difference between .308 Winchester & 7.62x51mm NATO?
  11. madcratebuilder

    madcratebuilder Well-Known Member

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    Depends on bullet weight.



    Most semi-auto 7.62 nato chambered rifles well shoot both .308 and 7.62. You have to pay attention to the bullet weight when shooting .308. Heavy bullets can damage parts on semi's. Most are safe with up to a 175gr bullet.

    Another thing to watch for when shooting .308 in a semi is the commercial .308 has a soft primer compared to the 7.62nato and you may have a slam fire. Always have the muzzle pointed down range when chambering a round.
  12. Cougfan2

    Cougfan2 Well-Known Member

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    Sounds like you have it figured out. FYI, I called DPMS after I had purchased my DPMS SASS used and had pretty much the same question. DPMS confirmed that I could use either 7.62 X 51 or .308 ammo with no problems in their rifles.
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  13. Jamie6.5

    Jamie6.5 Well-Known Member

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    I hope those with re-arsenaled small ring Mausers from Spain etc. that were converted to 7.62x51NATO don't read this thread and think they are good to go.
    The SAAMI spec of 62K PSI on the .308Win could potentially cause them a lot of grief, and maybe some body parts!

    Cartridge Pressure Standards
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  14. madcratebuilder

    madcratebuilder Well-Known Member

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    This is a myth!

    Read this paper that FALPhil wrote several years ago.

    I couldn't post the carts, if anyone wants a copy of this pdf pm me and I'll send a copy via email.


  15. Blitzkrieg

    Blitzkrieg Well-Known Member

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    Important distinction. Never assume
  16. Sabertooth

    Sabertooth Active Member

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    Well done and clears up a lot. Also answers some of the question I had about the two.
  17. cwegga

    cwegga Active Member

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    So the end result is that it is still UNSAFE but not necessarily because of pressure...
  18. jake2far

    jake2far Active Member

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    The difference:
    1. .308 headspace, 1.630-1.634
    2. 7.62x51 headspace, 1.635-1.6405
    3. .308 case is thinner at the base of the case
    4. 7.62x51 is thicker at the base of the case
    The original 7.62x51 was designed for full automatic machine guns, it needed greater clearance in the chamber for reliable feeding, firing, and extraction of the cartridge; the thicker case allows for more stretch during firing, keeping the head of the case attached to the rest of the case during the violent extraction.
    In a nut shell if your weapon is marked 7.62x51 it would be a good idea not to fire .308 ammo in it until you find out what it headspaces at, if your weapon is set at the longer chamber dimension for the 7.62 (1.637+) and you use a thin walled .308 it could result in a head seperation. If the chamber measures in the standard .308 area to tight 7.62 (read 1.630-1.635) it is safe to fire .308 ammo in a 7.62x51 marked weapon. The pressure is the same, but the chamber dimensions are not.
    Hope this helps

    Jim
  19. BrentN

    BrentN Active Member

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    I recently bought a Ruger Scout, .308, and have been researching this myself to make sure that x51 will be safe to plink with. Jake's post seems to be on the money from what I've found concerning the headspace. I'm also looking into reloading, and it seems there may be issues with brass fired thru a "loose" x51 chamber, then being reloaded for .308. Neck trim and case life come to mind. Please correct me if I'm off track.