Hello Fotis, I shot 12 grs of AA#7 powder in my original '73 Winchester in 44-40, yes, .427" cast bullets are what I used too, sized down from 44 mag bullets at 240 grs and .430"
Velocities were in the 1200 fps range in the rifle, shot through both shoulders of a doe so fast at 55 yards she didn't know what hit her, she stumbled then trotted 35 yards and crashed in the leaves.