Well, I got out and put some loads thru the 24" 700 XCR 375 Ultra today. 260 AB bullet, rem 9.5M primer throughout.
IMR 4350--
94 gr-2881 FPS 3 shot group 1.730
96 gr-2950 fps 1.840
Both loads put the first two right together and the 3rd shot way out. I'm gonna seat the bullet deeper and try again.

H4831 SC
97 gr-- 2750 1.30
99 gr-- 2815 3.00+ probably me! smile
101 gr- 2860 1.530
The 101 gr load also put two right on top of each other and threw the third way out.

15 rds seemed to be my limit today from the bench with such a light rifle. (I seriously doubt it goes 9 lbs all up--more like 8.5 lbs) It was a handful. Its showing good promise of being a real accurate 375 though.