I shoot a .260 AI for F class comp. On my 2nd bbl I decided to stray from my typical load w/ a 139 Lapua and H4831SC. My buddy and I split a case of 10- 1 lb jugs. I used some of 1 of the jugs for load dev. and found that I got slightly higher velocites (50-75fps), but my barrel/ chamber/ rig liked the H3831SC slightly better in terms of accuracy. Very slight difference at 300yds in group size, but enough to make me think that at 600 and 1000yds, it might make sense to stick with what I have used for 3 years now. It does what they said it would , increase velocity. In my bbl though- 28" Shilen Sel. Match, 8 twist, It was slightly more accurate with H4831sc.