I have found a good load for my CZ 550 in .416 Rigby. It consists of the RCBS-style 350-grain flatnose gascheck bullet sized .417", Brinell 22-25 hardness, with 112 grains of AA8700 powder, Federal 215 primers, in Jamison cases. Bullet seated to crimping groove.
This load groups about 1.5" @ 100 yards. IV @ 10' from muzzle = 2100 FPS.........