85 grains of RE25 seems to work well for me. I've copied and pasted the info provided from Berger.
7mm Remington Ultra Mag
(COAL - 3.600"; Barrel Length - 26")
Bullet Powder Start Load Approximate Start Velocity Max Load Approximate Max Velocity Fill Ratio
168 Grain RETUMBO 84.5 3029 88.5 3151 93.7%
168 Grain VIHT N170 84.5 2840 89.3 2994 96.1%
168 Grain NORMA MRP 2 80.5 2881 84.8 3014 90.3%
168 Grain H870 90.0 2982 95.0 3160 96.9%
168 Grain VIHT 24N41 93.5 3028 98.0 3193 97.9%
168 Grain 50BMG 94.5 3012 98.8 3195 102.9%
168 Grain AA 8700 96.0 2945 100.5 3107 102.5%
168 Grain IMR 7828 77.5 2996 81.2 3124 88.3%
168 Grain RE- 25 81.0 3010 85.4 3146 91.4%
168 Grain H1000 81.5 2876 86.0 3017 92.6%
168 Grain US 869 92.5 2894 97.3 3052 100.3%
Sorry about the formating, I copied it from an Excel spreadsheet.