buddy got his son into shooting blackpowder this yr, and I recommend using the 200gr shockwaves for is 50 cal, and experiment with powder charges from 65gr to 90gr to see what flies best and what he is comfortable with.

I shoot the 250gr shockwaves in both of my 50 cals and 200gr shockwaves in my 45 cal all being pushed with 90 gr of powder