After modifying the hammer on my Colt clone to a solid design I sought a method to safely carry six rounds. http://thefiringline.com/forums/showthread.php?t=459200
Taking a cue from the old Manhattan Revolvers I cut a safety notch on the cylinder. It turned out pretty well and the cylinder locks up tight in the safety position. Unlike the Manhattan, however, I only cut one notch as opposed to the six they used. http://www.relicman.com/weapons/imageweapon/W1201C.JPG
Cylinder was first marked with dental pick to ensure proper location of notch.
The notch was cut free-hand with a Dremel tool, small drill and milling bits, mini files and a small sharpened screw driver used as a finishing tool. Cylinder was re-blued with chemical bluing agent after modification.