I suggest that you go to the North-South Sirmishers Association bulletin board.
www.n-ssa.org
There are special "Sharps Loaders" out there, which many Skirmishers use for competition. The N-SSA outlawed paper cartridges long ago due to fire hazard on ranges. Several "suttlers" such as North East Trade Company have Sharps Loaders.
The 1863 Sharps tends to be one of the most contankerous guns out there. Unless you take special care to properly grease the gas wedge seal, it will not work properly and you will get gas in your face. They also tend to be contankerous accuracy wise. In general, its much easier to get a good musket to shoot accurately than a Sharps. Also, in comparison to a musket, the Sharps takes about 4 times as long to clean. The N-SSA guys are the experts and they can tell you all the tricks to getting these guns to shoot. Once guys figure these guns out, they tend to love em- but till then, I would not stand between a tree and a new Sharps shooter.... The only thing more frustrating is getting a smoothbore musket to shoot.