Lloyd,
Are these 1860's you want to convert??
I use Uberti's, the ASM would be good too, I tend to stay away from Piettas because their over all specifications are not very close to the original Colts..... and they tend to over harden their frames. Now thats just my preference.
The cylinder on this one is the original percussion cylinder. You have to chamber the gun at a slight angle to keep from getting into the cylinder stops, I have a jig set-up on a rotary table that I use for this.
Bill