Originally Posted by TreeMutt
J O'Connor said, in his opinion, the accuracy of a hunting rifle should be judged by a 3 shot group....
Originally Posted by Jordan Smith
Originally Posted by TreeMutt
I just conjured up a load for my Ruger 77ST, 30-06, old tang safety model, mounting a fairly new Weaver Classic K6X38 scope that I don't think I'm going to tinker with anymore (yeah right smile

It's no screamer but it's really accurate. 48.5 grains of IMR4064 behind a Sierra 165 HPBT Game King in a Federal case, CCI 200 primer, OAL 3.200. I'll get around to measuring it's speed soon.

Several 3 shot groups into nearly one hole or maybe I better call it 1/4" capable if I really do my part. This is unusually very good for me and this rifle.

My question is; the zero for this load is about 1/8" inch from the center of the aiming point at 100 yards. Any idea where this bullet will impact center because of spin drift, if it ever will? ......Thanks, JJ


Your zero is 1/8” from POA in which direction? What ROT is the barrel? Assuming RH twist barrels, I often favour the left of POA when I zero at 100 meters just to offset spin drift farther downrange. Fast-twist barrels induce more spin drift than barrels with a slower twist rate. In your case, assuming a 11” twist rate, 2975 fps at the muzzle, SAC, and a 100 m zero, spin drift causes 2” of deflection at 500 m and 15” at 1000 m. In angular units this is about 0.1 MRAD/0.3 MOA and 0.4 MRAD/1.3 MOA, respectively. If instead of zeroing right on at 100 m you zero 0.3” left of POA, spin drift will be reduced to 0.5” at 500 m and 12” at 1000 m, or 0 MRAD/0.1 MOA and 0.3 MRAD/1 MOA, respectively.


I think this response was directed at the wrong person...