30-06 vs. 30-378

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by hemiford, Mar 5, 2014.

  1. hemiford

    hemiford Well-Known Member

    Oct 7, 2013
    In this post I am touching on several BIG topics, but I'll try to sum them
    up with one question.

    22" barrel length is common to many 30-06 rifles. Since a 30-378 Wby
    has very close to twice the powder capacity, why doesn't a 30-378 rifle
    have a 44" barrel ?? This would give each rifle the same expansion ratio.


    On a side note, this should also give the 30-378 bullet about 1.414 times
    the muzzle velocity of the 30-06 (same bullet weight).
    I.E., 3800 fps vs. 2700 fps.

    I have done a lot searching to find graphs of the internal pressure traces
    of large capacity cartridges, to compare with a typical 30-06 pressure trace,
    and have not found good comparative results.

    I have done this with gasoline engines and compression ratio, which is a
    VERY similar situation.

    Aside from the inconvenience of carrying around a very long barrel, I see
    this as a simple engineering exercise in scaling.
  2. MudRunner2005

    MudRunner2005 Well-Known Member

    Oct 13, 2008
    Wow...That scared me when I saw the title. I thought you were wanting to compare the 2 ballistically. :D

    I was gonna say, that's about like comparing a slingshot to a tomahawk missle. LOL

    The .300 Sherman is a better ballistic comparison than the standard .30-06. But they're still far apart.

    Also, the .30-06's really will shine with a 26" barrel.

    The reason they don't need a 22" vs 44" barrel is because even though it has twice the powder, the powder won't burn as fast creating more pressure to push the bullet faster, therefore it doesn't need a 44" barrel. The .30-06 will use a faster burnng powder only requiring a 22-24" barrel to reach good velocities.

    LONGSHOOTER Well-Known Member

    Oct 21, 2007
    You talk as if these processes are to occur in a linear fashion.

    My suggestion? Keep studying.
  4. Michael Courtney

    Michael Courtney Silver Member

    Nov 15, 2010
    If you're going to get the same efficiency with the same bullet weight, you'd need a much longer barrel.

    Overbore cartridges are much less efficient, but it helps that most overbore cartridges are used with longer, heavier, high BC bullets. A 208-230 grain bullet can use the extra powder in a shorter barrel length than a 150-165 grain bullet.

    But adding more powder capacity and much greater powder charges to a cartridge is almost always a situation of demishing returns.