John, I bumped the Varget, with the 250 AB, up a grain to 61.5 and still was not quite to your speeds. I am guessing if I took it all the way to the extreme you mentioned of 62 grains, I'd probably be about where you were.
But the really interesting (and validating, to your "rules") news is I dialed in on the load of 2000-MR that gives the velocity I had estimated using your rules in the OP. Here's the result of the original math: "In summary, I ought to work up to ~67.8/2000-MR for ~2670 FPS with the 250 NAB"
Well , tweaking around I finally settled on 68 grains of 2000-MR. I fired 8 rounds today and the average speed was 2668 fps (with an SD of 10 for the 8 shots). So that is within 2 fps of what your rules predicted at only 0.2 grains charge different from what the math indicated, in transposing my success with 2000-MR with 250 grain bullets in the 35 Whelen AI to 250 grain bullets in the 9.3x62.
I'm thinking that's close enough for government work.
Thanks for the guidance,
Rex
