I have two heavy loads that I used in my 7 1/2" bbl RH. But with Starline brass.
The Lee 340 gr 45/70 bullet, sized to .4525. It casts 335 gr in my #2 alloy. I get 1340 fps with 23.0 gr 296. 1.78 COAL.
The other is the 300 gr Hornaday jacketed 45/70 bullet, re-sized to .4525 and 25.0 gr H4227 for 1400 fps. 1.78 COAL
Both shoot 1 - 1 1/4 @ 25 yds.
I got the RH to shoot Casull level loads and the 25.0 gr H4227 load is the bottom end 454 Casull. I didn't go higher because that is all that I can hang on to! I felt bad for the paper, too. It didn't deserve the extreme abuse
Frank