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General ballistics for the K31

Discussion in 'Rifle Country' started by Snowdog, Nov 10, 2003.

  1. Snowdog

    Snowdog Well-Known Member

    Can anyone give me a rough description on the ballistics of the cartridge used by the K31 (bullet weight, muzzle energy and velocity). If I'm not mistaken, this would be the 7.5 Swiss.

    I am assuming it would fall in the power catagory of a mild .308win.
    Any ideas?

    While we're at it, how about a description on the 7.7 Jap.

    Thanks in advance.
  2. AV1611

    AV1611 Well-Known Member

  3. natedog

    natedog Well-Known Member

    7.5 Swiss is more like a .308 Ackley Improved. It has a very sharp shoulder angle.
  4. Navy joe

    Navy joe Well-Known Member

    My V-V/ Lapua(that's a Finnish word fer 'spensive) reloading guide lists some 7.5 Swiss loads as well as several pages of .308 offerings. Pushing a 167 Scenar(match boattail) the guide lists a 49.2gr load of N150 as the max, achieiving 2740 out of a 23.5' 1 in 10" barrel.

    For .308 with the same bullet it lists N150 of 46.1gr as the max with a velocity of 2657 from a 24" 1 in 12" bbl.

    So, ballistically similar. Looking at the cases you are about halfway in between .308 and .30-06 in the case capacity and length department. Uses the same bullets.

    Incidentally, the max specs they give for the same bullet and powder in -06 are 52.1gr max, 2694fps out of a 24" 1 in 10". Kinda gives credence to the whole idea of the long skinny case rounds being less powder efficient.

    Having fired a total of 19 rounds, 7.5 Swiss may become one of my favorite rifle rounds. Already planning on a second K-31 and reloading. who knows, if I ever get the time to wear out a .308 bolt gun maybe I'll have it re-barreled in swiss.
  5. Navy joe

    Navy joe Well-Known Member

    Finally having a 60 round pack in the house; I went ahead and pulled one down. The bullet in the GP11 is a FMJBT with cannelure. One heck of a boattail on that thing too. Weight is 175gr. Powder was approx 48.5gr of a stick type. I believe that I saw on Swissrifles.com that this stuff is rated at around 2650 muzzle.

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