I have slugged the chamber throats and bores on both my Redhawks. .4315 groove dia and .433 dia throats on both guns (+/-.0001.) My go to load for both is the Lee 310 gr gas check bullet sized to .433 from clip on wheel weights with 4 oz of tin to 20 lbs lead. I drop them from the mold straight into a bucket of cold water to harden. 21.5 gr H-110, Federal 150 (standard large pistol) primer, all stuffed into Federal cases trimmed to 1.280. That bullet has two crimp grooves and I crimp them long. I average just over 1200 fps from my 5.5 inch gun and get a bit more from the 7.5. Both guns will print 1.5 inches at 50 yds off sand bags.
Some sources claim that H-110 and 296 are the same powder. My experiences have not found that to be true. It could be attributed to different powder lots. I have good quantities of both, the H-110 being older. I use a standard primer as opposed to the recommended magnums because I get more consistent velocity with the standards. There isn't a deer, elk or black bear that will stop that load. I've shot a lot of critters with this load. They are either DRT or I see them fall within 50 or so yards. Stevie Wonder does my tracking.