Are you planning to re-enact? That will have some effect on your choices. The minies like a longer barrel as they need the extra length to get up to a decent velocity. The carbines are handy, but limit range. I'd go with a full length rifle-musket. Generally, carbines were the province of cavalry and troops with occupations that put combat second, such as sappers. Consequently, long range accuracy was of less importance. I had a J. P. Murray carbine years ago, and it gave good service, but even at 100 yards accuracy was lacking compared to the rifle. It actually was pretty good with patched ball loads, though.