S&W 15 intermittent hammer jam/ timing off

[rustypigeon]

I have a problem with my SW15 (made in 1967) that occurs on a very intermittent basis. Sometimes when I cock it single action, the hammer jambs at about the halfway position. Today I opened it up and cleaned and lubed the internals. I put it back together and was able to get it to do it a couple more times. I tried holding the revolver in different positions to see if I could get it to occur regularly but couldn't. What could cause this? I bought it used a few years ago, but it has not been used heavily.

Also the timing is slightly off on a couple of chambers. If I drag my finger on the cylinder, I can get it to cock without the cylinder fully locked. This is only a couple of chambers, and the rest are just fine. It is only off very slightly and it always locks when it spins freely (without dragging my finger on it). Any easy fix for this other than fitting a new oversized hand? Since most of my cylinders are fine, would an oversized hand cause problems with the cylinders that are timed correctly?

 

[armorer951]

Check the movement of the cylinder stop during the S.A. cocking operation to see that the stop is always being pulled down fully prior to the cylinder beginning to turn. The bevel on the stop or the tongue on the trigger may be worn sufficiently to cause the stop to not drop down properly, causing the stop to catch in the cylinder.
Reference your timing question....."carry up" is checked at the factory by cocking the gun slowly in single action to see if the gun locks properly on each cylinder. The gun should be clean, properly lubricated, and the cylinder unimpeded when timing is checked.
An over-sized hand will cause a change in the overall timing of the gun and will require fitting. It might be easier to mic the existing hand's width and substitute a slightly larger part, +.001-.002. This substitution of a slightly larger part might help the carry up without additional fitting.

 

[rustypigeon]

I figured out what was causing the jam. When the cylinder rotates, the rim of the cartridge gets caught on the machined ridge on the frame. Here is a picture of the ridge on the frame and a snap cap jammed on the ridge with the hammer half cocked.