I was loading for my 6.5" raging bull in .454 casull, and did some test loads using 200 grain cast bullets.
Starting at 31 grains of H110, I was getting good velocities around 1500+fps. I moved up from there, but once getting up to 33 grains, the muzzle flash was huge, lots of flame out the barrel. These loads would definitely need a longer barrel to be fully effective. I made my way up to 35 grains at which I was getting up to 1800+ fps at 5 feet from the chrono. I would expect higher velocities with jacketed bullets, I just had a lot of cast lead lying around, so decided to make some test loads. The 33 grainers delivered the most consistant and seemingly efficient load for this barrel length, though that is where the high muzzle flash started.
Even when loading to the top end, my RB has handled all the loads I have put through it just fine.