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more free brass questions.. 308/762x51nato

Discussion in 'The Ammo & Reloading Forum' started by soundguy, Jun 9, 2012.

  1. soundguy

    soundguy Well-Known Member

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    ok.. mor closet cleaning has yeilded 4 50rnd baggies of spent casings. baggies are marked 7.62x51us nato I haven't been over to see if crimped primers or not.. but that's not an issue if they are.. I have a reamer.. etc..

    I know there is a sammi pressure spec difference and the .308win is like 12kpsi 'hotter; and thus not to be fired in a 762x51 nato chamber.

    now.. what about the brass? can bras that was 762x51 fired, be ran into a 308 after usual prep. ie.. full length resize and trim?


    again.. i can get the brass free just by driving over... I do have .308w rifles.. but no 762x51

    opinions?
  2. jlloyd73

    jlloyd73 New Member

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    I would just verify if they are Berdan primed or not......if they are they might not be worth more than scrap. I would get it regardless.

    It has always been explained to me to be the same.....308 and 7.62x51
  3. JLA

    JLA Well-Known Member

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    Exactly right soundguy. Brass is brass as long as the proper loading procedure is followed.
  4. Bindernut

    Bindernut Well-Known Member

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    The only major thing I've noticed different about reloading some 7.62x51 NATO-stamped brass is that they might have reduced case volume compared to commercial .308 brass.
    If you're running a near 100% load density powder or higher (IE a compressed load), be sure to back off a bit and work your load back up for the reduced case volume.

    I've seen the same thing between 5.56 and commercial .223 brass as well.
    For this reason, I still prefer to segregate military and commercial brass.
  5. soundguy

    soundguy Well-Known Member

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    cool. yep.. I hear ya on reduced case loads. I have a few powder choices and feel i can work upsomething in a non compressed load. i think even 4064 will go uncompressed.

    will for sure check the primer type. I always look down in with a bore light and look for a central flash hole vs the lil side holes inthe no-no berdan stuff.

    same people gave me the 350 30-30 rounds I jsut painstakingly deprimed, sized and trimmed. OOF!

    now a couple hundred 308ish stuff. i got more brass than I can reload.. :)

    if any of it is berdan if can go in my trashbrass bucket that I'll save for recycling..

    i was figuring it was essentially no different brass.. except for possible thicker and a crimped primer pocket.. maybee. figured I'd ask before doing anything stupid though.

    say.. I gotta find more friends that used to have spouses into relaoding.. and keep scooping up the free leftovers :) all i gotta do is go claim it now. ;)

    thanks guys.
  6. JLA

    JLA Well-Known Member

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    One of my fav .308 loads in 7.62 nato brass is 42.7 gr IMR4064 under a 175 SMK and a Federal GMM primer. Pretty much Federal GMM 175 gr duplicates that fit YOUR rifle. ;)
  7. steve4102

    steve4102 Former Guest

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    Yup as above, some 7.62 brass will have reduced case capacity. It's best to measure your case capacity in grains of H20, that way you will know for sure.

    As for pressure.


    The pressure in the .308 and the 7.62 virtually identical. The 308 runs at 62Kpsi the 7.62 Nato runs at 50K CUP not psi which equates to about 62K psi. The 7.62 was never testing in psi it was tested in CUP and some dumb ass in the US Military exchanged the CUP for PSI in an official document and has cauised mass confusion ever since.

    If you look through military ammo specs from before the mid-90's, you find military copper crusher numbers reported as "psi" at the same time a commercial maker would have reported them as "CUP" (I don't know why "CUP" gets caps while "psi" gets lower case, but that's how SAAMI publishes them). The SAAMI conformal piezo spec is 62,000 psi MAP (Maximum Average Pressure). I'll have to check, but I recall SAAMI MAP allows up to 4% deviation from average, so 64,480 psi would be the allowed extreme spread in SAAMI compliant ammo.

    The NATO allies use 415 MPa, which the CIP uses for both 7.62 NATO and .308 Winchester. That converts to 60,191 psi, but the CIP measuring system sets the sample point further forward in the case, so it sees a bit of the pressure drop at the bullet base that occurs when the bullet starts moving. That makes them tend to read about 2,000 psi lower than the SAAMI setup does in this pressure range. So the same ammo would measure closer to 62,000 psi in SAAMI equipment.

    http://www.ar15.com/media/mediaFiles/348/32231.JPG

    Now take the load data from the document above (172gr bullet, 44gr IMR-4895) and compare it to some 308 Win data in your loading manuals. You will see that there is no way that this load of 44gr IMR-4895 can be running at 50K PSI. It is Running at 60K PSI or 50K CUP.


    You can also go to Midway and check out their ammo. Note the Federal 7.62 ammo has identical ballistics, fps, fpe as the same load in 308 Win. Only way these two can have the same ballistics is if they are running at the exact same pressure.
    http://www.midwayusa.com/product/95...nition-762x51mm-nato-168-grain-open-tip-match

    http://www.midwayusa.com/product/95...grain-sierra-matchking-hollow-point-boat-tail


    http://how-i-did-it.org/762vs308/chamber.html
  8. soundguy

    soundguy Well-Known Member

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    that was going to be my next question. I know in my manuals there are different laoding specs for m1 garand and 30-06 springfield. but I havn't specifically looked if there was a seperate listing for 762x51 vs 308w

    and if there was. would there ben any problem loading to the lower ( assumed ) 76251 spec and shooting that in a 308 chmabered weapon? ( if I had a 762.. which I don't know if I do or not.. ;) )
  9. JLA

    JLA Well-Known Member

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    beautiful Steve. :thumbsup:
  10. steve4102

    steve4102 Former Guest

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    The Garand specific data is due to the rifle design not the chamber specs. The Garand Gas system requires powders that are on the fast to medium side of the spectrum for the 30-06. Burning slow powders in the Garand can allow to much gas to enter the gas port resulting in a bent Operating Rod or damaged bolt. Port pressure is not the same as chamber pressure, nor are there direct corollaries: low chamber pressures do not necessarily mean low port pressures, and vice versa.
    Last edited: Jun 10, 2012
  11. steve4102

    steve4102 Former Guest

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    If you find a manual that list specific load data for the 7.62 NATO chamber, please post it here I would like to see it.

    I have Speer, Sierra, Nosler, Hornady, Lyman and of course the Powder Manufacturer's data and none of these list any 7.62 data, only 308 Win.

    OH, cept one Lyman 48. At the top of the page in Bold letters is says 308 Winchester followed by small cased letters (7.62 x51) (7.62 NATO).
    Last edited: Jun 10, 2012
  12. gdmoody

    gdmoody Moderator Supporting Member

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    The Hornady #7 manual lists 308 Winchester loads and then the next section is 308 Winchester Service Rifle. Now, that doesn't specify that it is a 7.62X51 load at all but it does say that it was for the M1A or M14 which would lead one to think that it is.

    The speer manual has just 308 Winchester and the Lyman has exactly what Steve said.
  13. JLA

    JLA Well-Known Member

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    And the reason for that is similar to the reason for Garand specific data. The gas system could be damaged by .308 win hunting loads in an M14/M1A
  14. soundguy

    soundguy Well-Known Member

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    i gotta set down an look mine over now. i have lyman 49, and speer, sierra,nosler, and hornady 7, and a few imr and some magazines..
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