I have an 1860 army, Pietta.
The little block that comes up from the receiver to hold the cylinder still has stuck up. This is causing the cylinder to be scored.
I removed the cylinder. If I push down just a little on this little block, while cocking the gun, I can feel the mechanism "catch", and it will recede into the receiver as it should.
Let the hammer down, cock it again, it will fail to drop down. You have to push on it just a little each time, then it will work.
What is wrong with my gun? Sounds like failure of another Pietta spring.