I suppose it could be done in an emergency. The danger would be if some powder got down into the action and was ignited by blowback from the chamber. The Conant gas check, which is part of the breechblock face, would work...unless it was badly fouled or corroded. If I were trying the loose powder and bullet, I would certainly want to be wearing eye protection, and maybe even some type of shield for my face! The likelihood would be if you ran out of paper cartridges, you would probably not have any loose bullets and powder anyway. As good as the Sharps percussion guns seemed to be (at Gettysburg on the first day), if I could get my hands on a Fifth Model Burnside and at least a gas check, if not the conical cartridges, that would be my choice!