My pet load for that gun was 80 gr 777 ffg under a 225 gr pure lead Buffalo Bullet in the yellow sabot, but it would shoot equally well with .490 prb's. Ignition was fast and reliable. I never had a problem with over compression but I don't stand on the ramrod either. My rod was marked so as long as the bullet stops at the mark, I don't need to give it that little extra push. I have since gifted that rifle to a friend and I'm not sure those bullets are even still made.
FWIW, after trying a lot of different bullet/gun combinations, my three goto projectiles are home cast maxi balls, paper patched conicals and prb's.