Colt made several models of revolving rifles, carbines and shotguns in the 1838 to 1841 time frame. They revived the idea with the Model 1855, which was made as a musket, two different types of carbines, a shotgun, and three different models of sporting rifle. (This does not include shoulder-stocked pistols, which were another category.) The 1855 was a Root sidehammer type, and the gun pictured, while it does not conform fully to any of the original guns, is overall very similar. The Colt muskets were made in .44, .56, and .64 caliber, with the latter being very rare. Carbines were made in .36, .44, and .56.
Chain fires undoubtedly happened, and were usually caused by badly fitting balls, not by detonation of the percussion caps. No percussion revolver ever was made in such a way that the caps could come in contact with the recoil shield. Our ancestors were not that dumb.
BTW, it is repro manufacturers who have chosen to eliminate the safety pins from Colt type revolvers; I wonder what they think the hammer notch is for.
Jim