issue with ASM 1860 cylinder operation

[W.J. Cogg]

one of my two open tops, a ASM 1860 .44 caliber of unknown vintage at this time

if the barrel is pointing parallel to the floor and downwards, everything works as normal:  cock the hammer, cylinder rotates, trigger drops hammer.

now...if we tilt from 10 degrees upwards of pure vertical and the hammer is cocked, the cylinder doesn't turn.  Everything appears tight. I haven't disassembled the revolver yet.

Doing a google search and overlooking schematics, I stopped and thought to ask here first if there is a simple fix. very new to revolvers.  I'm generally into the AR/Glock/AR area.

suggestions?

[Abilene]

That is the classic symptom of a broken hand spring.  Pointing the gun downward lets gravity push the hand forward into the back of the cylinder.

[W.J. Cogg]

hand spring, fantastic thank you!

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[Lefty Dude]

You may consider installing a hand spring plunger, as per the Pettifogger modification. All my C&B are modified for this hand spring replacement.

[Flint]

This is an Uberti Opentop, but the principle is the same, spring and plunger are Ruger parts.  Hole and diameter as Ruger.  The set screw is not necessary, the backstrap will hold the spring in place as it does on the Ruger, but can be used for a bit more spring tension.