i would go w/ maxi-ball style bullets, which usually weigh about 240 grains in .45 caliber. either the t/c maxi-ball/maxi-hunter or if he casts some of the lee REAL's. not sure if buffalo makes bullets in that caliber or not.
option two is to try some mmp sabots w/ 200 grain xtp's. that might work in the 1-48" twist, then again might not work so weel. i havent tried sabots in my renegade or grehawk, so im not sure.
w/ either of these loads i'd start w/ around 90 grain ffg blackpowder or pyrodex and work up and down till he finds the right load. 90 grains has always given me the best results in my renegade. you might prefer fffg, itll give a little better velocity (and higher pressure and a little less fouling).
you can use a roundball, but i wouldnt use it past about 50 yds. those .440 roundballs only weigh about 130 grains.
im sure cayuga will have some good loads for ya as well.