keith,
With the 7.9 mark your rifle is likely intended for 8x57IRS(.323"bullet),but it could be 8x57IR.Unlike shooting 8x57IRS ammo in some 8x57IR rifles,shooting 8x57IR ammo in 8x57IRS rifle is safe. At the worst, it won't be as accurate, and if you shoot a lot of it,there may be some "gas cutting.You can find out by "sluging" the barrel.IR barrels are usually .318-.320",sometimes a little more, in groove diameter.
Mike

Last edited by Der Ami; 03/26/15 04:43 PM.