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7.62 X39 vs 6.8mm Remington SPC

Discussion in 'Reloading' started by MinervaDoe, Oct 9, 2011.

  1. MinervaDoe

    MinervaDoe

    9,253
    1,512
    Jan 26, 2009
    San Jose, CA
    I was looking at my Lyman manual, and I noticed that the difference in velocities for the 110 grain bullet is only about 100 fps.

    I also noticed that the manual uses different powders for each cartridge.

    How do these cartridges compare ballistically?

    I've heard the 6.8 SPC is touted as a good cartridge for a short barrel rifle, that can reach out to 600 yards. But, would both cartridges be roughly equivalent in a Mini-14?

    Is the 6.8 getting its extra 100 fps by using fast burning modern powders?
     
  2. steve4102

    steve4102

    2,310
    674
    Jan 2, 2009
    The Ruger Mini-6.8 is cut with a SAAMI spec reamer. The rest of the world has scrapped the SAAMI chamber and adopted the 6.8 SPC Spec II chamber. The spec II has the proper throat dimensions allowing the 6.8 to run safely at it's designed 58K psi.
    Load data for the 6.8 with a 20 inch barrel runs a 110gr bullet at about 2600fps @58K psi. Load data for the 7.62x39 with an 18 inch barrel runs a 110gr bullet at 2675fps or about 2720fps with a 20 inch barrel.

    Mosley because it runs at a higher pressure than the x39.
     


  3. MinervaDoe

    MinervaDoe

    9,253
    1,512
    Jan 26, 2009
    San Jose, CA
    That's very informative. A little Internet searching finds this.
    6.8 SPC Chamber Drawings
    http://www.frfrogspad.com/68chambers.htm
    and this:
    The 6.8 SPC (6.8 x 43 mm) Cartridge
    http://www.frfrogspad.com/68spc.htm
    7.62x39 = 45,000 psi

    The tables in this article saved me a lot of reserch time.
    Thanks for pointing me in the right direction.

    :wow:
     
    Last edited: Oct 9, 2011