I'm using 101gn of Retumbo to push a 250AB around 2970. Work up to this in .5gn increments as I believe it's on the hairy edge of being over pressure and I won't use this load in temps over 50*. Anyway, here's the recipe:
250AB
Fed nickle brass trimmed to 2.74
GM215M
101gn of Retumbo
COL of 3.64 (measured from tip to base)
I load the 250 gr AB with 98.6 grs of Retumbo for a MV of 2950 fps and .5 MOA from my M700 LSS. The 250 gr PT has a MV of 3024 fps with the same charge.
i loaded my 338 ultra with 98g of h1000 and a federal 215 and a 250g AccuBond in a 28" tube to over 3000 fps. this was a little stiff so you may want to start around 96g. this load is what i used on my longest kill to date.