In the last rifle we did, we were running 69.0 grains of IMR 7828, Remington 9 1/2 large rifle magnum primer, Weatherby brass, and a C.O.L of 3.290". This was yielding velocity well over 3300 FPS from a 26" Hart barrel, and averaging aroun .3" groups at 100 yards. I use a match dimension chamber...