Last year a friend of mine got some 777 and used it in an original shotgun with no obvious problems, i was dubious about using it in my 12 bore as the grain size was so small (fffg) on the container were pressure ratings based on CUP (copper units of pressure) it seemed to me to be more a rifle or pistol powder, we could find no pressure data for 777 not even at the proof house, does anyone have any ideas what pressure the stuff actually generates?