WAM,
I have also published articles and book chapters about the problem with making accuracy judgments on 3-shot groups. Among other things, a professional statistician I'm acquainted with calculated that the average point-of-impact from several 3-shot groups will vary around .7 inch at 100 yards, which doesn't help much when calculating downrange spin-drift.
Will also note that Elmer Keith, who did quite a bit of long-range target shooting, and what was considered long-range big game hunting back in his day, preferred to sight-in his long-range hunting rifles 3 inches high at 100 yards--and half an inch to the left, to compensate for spin-drift with a typical RH twist barrel.
Thanks for that last nugget. DIdn't know that.
