The basics are to check the chamber alignment with the barrel at full cock. It should come up locked aligned at all 6 chambers. If the bolt is in the cylinder notch and the chamber is off center, the notches are off location, or the frame machining is off center. You can pull the nipples to let light in and cock the gun looking at a light source behind and look down the barrel to see if the edges of the chamber mouth are not visible beyond a hair. Then check the timing, it should at least be reasonable or tunable. If the bolt drops too soon, it will ring the cylinder with a drag mark, and only a new bolt will fix it if the bolt's wings are adjusted for sufficient tension against the hammer cam face and it still drops too early. An over=strong bolt spring can aggravate that too. A weak bolt spring can cause overtravel when you cock it fast. Make sure the parts all fit each other. If the mainspring is too strong, it can be tuned, but it cannot ever be as light as a cartridge single action, as the percussion cap/nipple/hammer system needs a harder hit than the sharper firing pin and primer of a cartridge system do. If the wedge is loose when the barrel has enough gap to the cylinder, you will need to adjust the wedge, but shoot it in first. Don't dry fire it with the cylinder in place, or at least remove the nipples first, so they don't get mushroomed from the hammer strike and then fail to fit the caps. Good luck with it all.