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7.62 NATO/.308 compatability

Discussion in 'Rifle Country' started by Blue1, Mar 7, 2013.

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  1. Blue1

    Blue1 Active Member

    Can 7.62 NATO be safely fired from .308 Win chambers? Can .308 Win be safely fired from 7.62 NATO chambers?

  2. 303tom

    303tom member

  3. HankB

    HankB Well-Known Member

    Generally yes . . . but headspace differences do matter; if you have a 7.62 NATO rifle with headspace on the long side of the 7.62 NATO spec, it may not be such a good idea to shoot .308 Winchester in the rifle.

    Here's a discussion of the issue from Fulton Armory:

  4. Trueno

    Trueno Well-Known Member

    Commercial chamber pressures generally run a good bit higher than NATO pressures. Keep in mind also that a lot of .308 bullets are in the 180-190 grain range and will beat up a semi-auto.

    PSL's, CETME's, G3's...I prefer 147gr 7.62x51 in em.

  5. Blue1

    Blue1 Active Member

    OK, but I'm just wondering if I can use the NATO round in my bolt-action Savage.

  6. Blue1

    Blue1 Active Member

    Ok, this is what I found in a Yahoo questions site:

    .308 Win vs. 7.62x51--The Straight Scoop
    Before we go much further, lets 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. That said, it is normally fine to shoot quality 7.62x51 NATO ammo in a gun chambered for the .308 Winchester (though not all NATO ammo is identical). Clint McKee of Fulton Armory notes: "[N]obody makes 7.62mm (NATO) ammo that isn't to the .308 'headspace' dimension spec. So 7.62mm ammo fits nicely into .308 chambers, as a rule." You CAN encounter problems going the other way, however. A commercial .308 Win round can exceed the max rated pressure for the 7.62x51. So, you should avoid putting full-power .308 Win rounds into military surplus rifles that have been designed for 50,000 psi max..... Reloaders should also note that military ammo often is made with a thicker web. Consequently the case capacity of 7.62x51 brass is usually less than that of commercial .308 brass. You may need to reduce recommended .308 Winchester loads by as much as 2 full grains, if you reload with military 7.62x51 brass, such as Lake City or IMI.







    Like the 5.56x45MM verses the .223? --- NOpe... Look here for info on that....



  7. USSR

    USSR Well-Known Member

    Sorry Blue1, but you've got it all wrong regarding the pressures. The 7.62x51 pressure spec's of 50,000 psi that you quote were obtained using the copper crusher method and are essentially C.U.P. pressure. The military is not beholden to SAAMI rules, so they can call C.U.P. pressures psi or banana splits if they want, but obtaining the pressure the way they did equates to about 60,000 psi obtained using SAAMI methods. So, there are no problems interchanging the two cartridges aside from perhaps differences in heavier bullets and slower burning powders which may not be compatible to M1/M14 platforms.

  8. madcratebuilder

    madcratebuilder Well-Known Member

    The pressure difference between .308 and 7.62 in insignificant. Much confusion from the different measurements, CUP vs PSI. There is not a reliable formula to convert one to the other. Head space and case wall thickness are the major differences.

    From a piece FALPhil wrote.

  9. Sav .250

    Sav .250 Well-Known Member

    I`d just go with the round it`s designed for. Peace of mind goes a long way.
  10. Reloadron

    Reloadron Well-Known Member

    Every now and then we like to have a thread on this subject. This thread is a good example.

    As has been pointed out the chamber specifications do vary in that a 7.62 NATO has what can be viewed as a slightly larger chamber. This allows a military rifle used under adverse conditions to be more forgiving in chambering a round. This is also apparent as was mentioned in headspace gauge dimensions being different.

    While in my experience the actual case outside dimensions have been identical. The military cases do have slightly less volume and have slightly thicker brass in the web at the bases of the case. I wish I had more 7.62 NATO factory loaded ammunition to measure as I was limited to some South African stuff.

    The pressures have also been covered in that a .308 Winchester cartridge is measured in PSI (Pounds Square Inch) while the 7.62 NATO pressure is measured in CUP (Copper Units Pressure). There is no simple cross reference between the two nor is there a simple math conversion formula. My understanding here is that there is really very little pressure difference.

    This is all on my summer bucket list. I hope to do an in depth study between the two for comparison purposes.

    Finally in the link is a picture of a box of .308 Winchester, that same box is also labeled 7.62 NATO as another member pointed out. Unfortunately the box end flap is not clearly visible in the picture. :(

    So my understanding is that while a .308 Winchester and 7.62 NATO chamber are not necessarily cut to the same specifications, the cartridges are identical as to outside dimensions. I have fired both in my M1A, AR10 and my Remington .308 bolt gun.

    Just My Take
  11. jmr40

    jmr40 Well-Known Member

    Short answer, for you use it won't hurt a thing. If you were trying to use commercial 308 ammo in a rifle chambered for 7.62 Nato ammo about the worst thing that would happen is that SOME ammo might not cycle reliably in SOME rifles.

    A lot is made of slightly different specs in ammo pressure and slighlty different chamber sizes. Pick any chambering, 243, 30-30, 30-06, 270, any of them, and you will find they are loaded to different chamber pressures depending on the manufacturer. Same with rifles. The tolerences between various rifles in any chambering can be just as great as the differences between typical 308 and 7.62 Nato rifles.
  12. chicharrones

    chicharrones Well-Known Member

    Just because photos are . . . photos. :evil:
    Last edited: Mar 10, 2013
  13. WardenWolf

    WardenWolf member

    The short answer is, a 7.62 NATO round will always work just fine in a .308, but a .308 round may cause problems in a gun designed for 7.62 NATO. The civilian loads are often a bit hotter, and have a wider range of bullet weights that can sometimes cause problems for semi-auto actions.
  14. Double Vision

    Double Vision Well-Known Member

    Thanks again Reloadron!
  15. Reloadron

    Reloadron Well-Known Member

    You're welcome Double Vision.

    What I would like to find is some Lake City and maybe a few other manufacturers of 7.62 NATO ammunition. This summer once the house bucket list is done I really want to drag myself and some instrumentation out to the range and do some experimenting.

    I want to chronograph some loads, especially identical loads in commercial and military brass. I also want to snag some data on pressure curves from different ammunition.

    Have to check out some gun shows for assorted 7.62 NATO stuff.

    I know what I should see and know it has been done before, just a few things I want to try. :)

  16. pseudonymity

    pseudonymity Well-Known Member

    I am not so sure about that. Take some .308 brass that has been FL resized a few times and put it in a 7.62 chamber that is long enough to close on a SAAMI spec .308 field gauge, and I think you are flirting with a case separation.

    .308 brass is designed to safely deform to a maximum length defined by SAAMI. A 7.62 chamber can be longer than that max SAAMI length and still be within NATO spec.
  17. 303tom

    303tom member

    So you are saying that .308 Winchester may cause problems for my semi-auto huh ?
    Last edited: Jul 14, 2013
  18. jonnyc

    jonnyc Well-Known Member

    "The civilian loads are often a bit hotter"

    Nope, sorry, just not true.
    As stated above, they are they same round and factory ammo is perfectly interchangeable. Commercial and military chambers are designed and spec'd differently, but the rounds are the same.
    Your mother is your father's wife, your aunt's sister, your kid's grandma, etc....same person.
  19. Trueno

    Trueno Well-Known Member

    aaaaaannnnndddddd.........we're off!

    I'll start some popcorn!
  20. SaxonPig

    SaxonPig Well-Known Member

    People keep arguing that they are not the same but I have never noted any problems firing one or the either from my rifles no matter what caliber is stamped on the gun. If there is any real difference I can't tell.
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