An 1860 Army with a full fluted cylinder was a legitimate Colt variation. The full flute is available from Uberti, and I also have one that is on a 2nd Gen Colt 1860 The problem that occurs with a full flute 1860 or 1861 is the bolt timing is absolutely critical. If the bolt drops too soon, such that it might put a ring on a standard round cylinder, it will hit the full flute in the rising wall, and lock it up, as the bolt spring is strong enough to overpower your cocking force pulling the hammer. It is a steep climb, and the bolt has to be timed so it drops EXACTLY at the very small leade to the cylinder's locking notch, or directly into the notch. That critical timing is the reason later cylinders were only half fluted. Easy way to check it out is to slowly cock the gun, and watch where the bolt drops (snaps back through the window), if it drops in the deep trough of the flute, it can't climb the slope to the notch which is at the largest part of the cylinder. If you can find an ASM standard round Army cylinder, swap it in to see if it solves the problem. If the bolt drops way too early, it will scribe that dreaded ugly ring around the cylinder. Try bending the ears of the bolt spring apart carefully, to increase the spring pressure against the hammer's bolt cam. An Uberti cylinder can probably be fitted. See VTIgunparts website for parts, cylinders, bolts, etc..
