That combo would be good out to 100 yards. I say that because I've killed several w/80g of Pyrodex (which is about the same load as what your dad is shooting)

If he is making good shoots on them i.e. not shooting them facing away from you, then you'll be just fine.

People don't seem to like the RB but when I think back, I believe I've probably had more boom-flops with a RB than I have any other bullet...