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308 vs 7.62x51

Discussion in 'Ammo & Reloading' started by stroker-c10, Apr 17, 2021.

  1. stroker-c10

    stroker-c10 Sharpshooter

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    This may be a stupid question but is there any advantage to the 7.62x51 cartridge? I ended up with a couple boxes of it and know that I can run it. Just curious if there is any reason why one might prefer it beyond availability. Thanks.
     
  2. dennishoddy

    dennishoddy Sharpshooter

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    Like most military brass, it's thicker. Because of that, there can be some minor adjustments if reloading that round vs the .308.
     
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  3. stroker-c10

    stroker-c10 Sharpshooter

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    Thanks Dennis. That was the general impression I got from reading. Slightly lighter powder load but no real advantage. Hope you and the family are doing well!
     
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  4. dennishoddy

    dennishoddy Sharpshooter

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    Doing great! Hope your experiencing the same!
     
  5. ShaneP

    ShaneP Marksman

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    A guy posted this on a Facebook group the other day.

    “History lesson on 7.62x51mm/.308W.

    Post WW2, the Army wanted a new rifle round, comparable performance to 30'06 Springfield, but shorter, for easier digestion by machine guns.
    Lighter weight would be handy also.
    Enter Test Cartridge 65.
    T65, Wildcatted from the .300 Savage cartridge.
    The T65 was developed along with the T44 rifle, which eventually became the rifle M14.

    T65 was a collaboration between Winchester Western and Frankford Arsenal.

    T65 went through several changes from T65E1 to T65E5 as the case was lengthened, shoulder angle changed, FA went to the thicker case walls at T65E2 and E3, this is why GI brass in this cartridge is so much thicker and lower case volume capacity.
    Also, T65 was developed using a new Double Base Spherical powder (product of Western division of Winchester), WC846, which we all, today, know commercially as BallC#2 thanks to Bruce Hodgdon buying surplus and selling it to our parents.
    T65E1 lengthened the case from 47mm to 49mm (the FAT(Frankford Arsenal Test)1 case)
    T65E2 tried a 30* shoulder, smaller extractor groove, thicker rim(FAT1E1 case).
    T65E3 went to a 20* shoulder and lengthened to 51mm (FAT1E3 case).
    T65E4 changed from a 150gr flat base bullet (basically a modified M2 Ball bullet) to a 145gr , longer ogived, steel cored, BT bullet in the FAT1E3 case.
    T65E5 was another minor bullet change, to a lead-core boat-tail.

    Essentially T65E4 was adopted as M59 Ball in 1955 which fought much of Vietnam and T65E5 was later adopted as M80 Ball we have had since 1959.
    M59 production stopped in 1960.

    Winchester released the completed cartridge to hunters and shooters everywhere in 1952 and, for wise marketing, hung its name on it as the .308 Wincester. Winchester went with slightly thinner case walls for slightly increased case powder capacity, civilian rifle chamber headspace tolerance being about 0.004" less than max allowed military headspace, case failure on first firing was not a concern.

    In 1954 NATO agreed to make the 7.62x51mm its standard small arms ammunition for rifles and machine guns.

    The ONLY difference between the 2 cartridges is an ALLOWANCE in military weapons to have (but not require) looser headspace before the weapon is required to be repaired. Minimum chamber headspace is identical.
    There is zero dimensional difference between the cartridges, they are fully interchangeable, and always have been, for 70 years now.
    GI ammo is loaded with a gunpowder that is NOTORIOUS among competition shooters for giving very high pressure in hot temperatures.
    GI ammo is tested to 140*F use.
    As such, it is loaded to ONLY 50,000PSI SAAMI (TM43-0001-27) at 70*F lab conditions to preclude excessive pressure damage if it is fired in very hot conditions. It is given "headroom" to increase pressure without concern or hazard to troops.”
     
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