I've been working up some 'target' loads for Dad's old 7mm Rem Mag model 70 Winchester- early post '64 version. I've seen quite a few recommendations for ~3.29" - 3.3" C.O.L., but for 175 gr SMK's this seems a bit short for my chamber. Via a Hornady overall length gauge, the SMK's engage the rifling at ~3.52" C.O.L. For accuracy, I typically see recommendations for a 'jump' of a few thou- maybe ~.005" to .012" at most; but this may be for target barrels / chambers.
At a 3.29" C.O.L., I can squeeze a .89" 5-shot 100 yd group out of the ol' gal under less than ideal conditions (some wind, only a 7X scope & tired eyes). That's not bad but I'd like to do better. Seems like a jump of .230" is pretty excessive and I'm killing some potential accuracy with this. I absolutely will not jam the projectile into the rifling to avoid a nasty over-pressure condition; but for reference, only ~.200" of the 175 SMK is seated in the neck at 3.52" C.O.L.
Anyone have any rules of thumb or at least advice regarding jump distance for magnum rifles with plain jane hunting profile barrels / chambers? Reason I'm doing this is to develop loads for a light hunter-class benchrest match. If anyone really does their homework for a SAKO, Kimber, Sendero, etc. light barrel rifle, they should be getting ~.5" groups at 100 yards. I'd like to be close to that. Yes, I swapped scopes and will use a VX-2 16 power scope instead of the old VX 7 power. As always, thanks!
At a 3.29" C.O.L., I can squeeze a .89" 5-shot 100 yd group out of the ol' gal under less than ideal conditions (some wind, only a 7X scope & tired eyes). That's not bad but I'd like to do better. Seems like a jump of .230" is pretty excessive and I'm killing some potential accuracy with this. I absolutely will not jam the projectile into the rifling to avoid a nasty over-pressure condition; but for reference, only ~.200" of the 175 SMK is seated in the neck at 3.52" C.O.L.
Anyone have any rules of thumb or at least advice regarding jump distance for magnum rifles with plain jane hunting profile barrels / chambers? Reason I'm doing this is to develop loads for a light hunter-class benchrest match. If anyone really does their homework for a SAKO, Kimber, Sendero, etc. light barrel rifle, they should be getting ~.5" groups at 100 yards. I'd like to be close to that. Yes, I swapped scopes and will use a VX-2 16 power scope instead of the old VX 7 power. As always, thanks!