First we need to know what state or states he hopes to hunt. The regulations for each state differ and some muzzleloaders are illegal in some states for hunting. Then we need to know what he wants to hunt (deer most likely). As far as inlines there are a wide variety of them but at this time my favorite new one available is the Knight Rolling Block which I do not have but would add to my collection if I didn't already have four inlines, two sidelocks, one flintlock, and two pistols. The new Knight RB will shoot both sabot loads (usually pistol bullets of less than bore diameter in a plastic bore diameter cup that the bullet fits in) and conicals (solid lead bullets that are bore diameter). It appears to be well thought out for design and function and several are reporting excellent accuracy and ease of cleaning. As far as caliber the first and really only choice that make any sense is .50cal. as the selection of bullets for it make it the way to go. It will do anything that the .45cal rifles will and some of them are very picky as to what they will shoot accurately. Many will recommend the T/C Omega which I have one. Personally after several years of owning it it is not my favorite rifle. It shot great at the start then the accuracy became erratic. I think it is due to plastic stock variation from shot to shot and from stock removal and reinstalation. The Omega plastic stock is a fairly weak link in an otherwise great rifle. The Knight RB would not suffer from that condition.