Never tried the 400+ grain bullets, but have been shooting a 335 out of my Bisley. I don't run them real fast. 20.5 grains of WW296 in Starline cases with Winchester primers yields about 1150fps. This is a very consistent load, and will go through pigs lengthwise.
My guess would be that the Bisley doesn't have a tall enough front sight for the 400+ gr. bullets, but that's just a guess. The 335s are quite comfortable to shoot in my gun.
Good luck.