I do cast my own, 240 grain tumble lube bullet from a Lee mold, sized .429, and loaded to 900 FPS. The same bullet shoots better out of my Rossi 92, but that rifle can't be scoped, the 77/44 can.
There is a note in the owners manual that best results are obtained with jacketed high velocity bullets, going so far as to say "avoid cheap cast lead ammunition", or something to that effect. Didn't see the same note in my 77/357 rifle owners manual.
So, I don't shoot a lot of cast lead through the 77/44, I have a Leupold 1 X 4 power shotgun scope on it now and with it I can hit out to 140 yards, the longest shot on my property. Using jacketed 240 grain bullets...