Though I'd share this with everyone, I just worked up a good load for my new BCA 50 Beowulf upper with heavy (MM 600 grains sized .502) boolit, PC with Eastwood Ford Light Blue. I'm using 32.5 grain RL7 with a Remington 9 1/2 primer. I forget the OAL but it's basically covering the 1st driving band. Haven't chrony'ed it, but expect about 1300 fps out of a 16" barrel. shooting grapefruit sized groups a 200 meters and a bit bigger than that at 300. kicks a bit, but fairly light rifle. hits like a sledgehammer, especially at 200m. no signs of overpressure, but would start lower and work up. I started with 31 grains and a Winchester large pistol primer and this wouldn't cycle the action. the 32.5 grain load cycles the action, and holds the bolt open on the last shot, but the primers are rounded and ejection is only a foot or so out of the rifle.
as always, YMMV and load at your own risk.