Originally Posted by
canross
Cylinder stop or hand is your culprit. They work in opposition to each other - the hand advances the cylinder in one direction, and the stop, well, it stops it over-traveling. If either is worn you will have rotational play in the cylinder, but the amount of play alone won't tell you which one is causing it.
If the hand is worn it should under travel and not fully reach alignment and have play.
If the stop is worn, it should reach alignment or slightly past alignment and have play.
Both may be worn, and it will not reach full alignment, but will also be able to move past proper alignment.
If it poorly aligns repeatedly on specific cylinders, especially under aligns, something might have happened to the ratchet on the cylinder. Usually that something is an amateur gunsmith. In this case, they've probably messed with other stuff as well, so you've probably got more problems to find.
To check which issue it is, place your weak hand thumb against the cylinder to provide friction, then very slowly and gently cock and let the hammer down with the trigger still fully back and see if the cylinder is under or over aligned with the bore. Avoid having your weak hand thumb move the cylinder when you do this. Once you have seen alignment, check if you can move the cylinder back against the hand, or forward against the stop to confirm what you're seeing.
Generally with a worn hand you'll find the cylinder is under rotated, and when you rotate the cylinder forward it will stop in alignment with the bore.
With a worn stop, the cylinder will advance to be in alignment or just slightly past alignment with the bore, but you can advance it past alignment by hand.
If both are worn, then it'll stop short of alignment, but you will be able to advance the cylinder past alignment as well.
Once you've figured this out, you can work towards repairing or replacing the correct part.
You may also encounter end shake (forward/back movement of the cylinder on the cylinder/arbor pin), and in really bad cases, fishtailing where the cylinder can move or twist side to side on the arbor pin. Some end shake is acceptable, generally a lot is not. Fishtailing is no bueno, only seen it on clapped out pre-1900's guns.
You'll also find a catch on the front of the trigger which keeps the cylinder from rotating while at rest with the trigger forward and hammer relaxed. This can wear as well, but it only affects the cylinder in a relaxed state, so if the cylinder free wheels when not in use, that's what's going on there. As long as it holds it's generally ok - it just keeps your cylinder from rotating when not in use so doesn't need to be rock solid.
