jaybe

amw_yo: Here is a comparison I just pulled off the internet from one source - you can easily find many others if you do a search for "black powder loads" or something similar.
* .50 cal180 gr roundball with 100 gr Pyrodex RS = 1863 fps at muzzle and 1380 ft lbs. energy. At 100 yds, this will be retainingabout 600 ft. lbs of energy.
* .50 cal 350 gr. maxi-ball with 100 gr Pyrodex RS = 1525 fps at muzzle and 1808 ft. lbs. energy. Att 100 yds, this will be retaining around 1200 ft.lbs. of energy.
From this simple comparison, you can see that with everything else equal, the roundball will leave the muzzle faster, but with less energy than a heavier projectile. It's trajectory will also be flatter, which will extend the "point blank" range (distance at which you can hit the vitals of an animal without raising your point of aim) over the maxi-ball, but it will also loose its energy faster than the maxi. So, in many ways, it's a trade off; the roundball goes faster, but looses its energy faster. The bigger bullet goes slower, but retains its energy longer.
As frontier gander said, as long as you limit your range (oh, he didn't say that, did he?), and get a good lung hit, you'll probably have no trouble killing a deer-sized animal out to 75-100 yards.
Personally, because of the distances I normally am able to see deer in the woods of Michigan, I prefer a heavier bullet (350-500 grain) that will carry more energy to the animal and therefore increase the chances of a cleaner kill.