I've used IMR 7828 with my .280 AI with a 26" tube but I found that Retumbo gave me better accuracy. this with the 168 Berger Hunting VLD.
Nosler brass CCI 250 168 Berger 65.0 grns. does a number on deer I'll tell you that!
I run 175ABLRs and 180 VLD Hunting on 60 of I7977 with a wlr. ~ 2800 FPS.
That's in both a 24 in M48 280AI and my custom 26+ in AI.
My " speed " load is a 140CT with 57.5 RL17 with a WLRM . That does 3200 in the 26 in pipe, and 3250 in the 24 (odd , I know)...
I have pushed 140s over 3400 in the AI, but I wouldn't recommend it.