Thanks for looking. Looked at one yesterday with usual seized piston head.
Seen lots of good info. on dismantle/assemble but unsure how it operates.
Cocks but won't release. Hammer? trips but snags second cam step.
Cocks/releases fully when set manually off the action.
Considerable spring force of main sear seems to be acting A about F to me
i.e. forcing sear into engagement with instead of out.
Explanation appreciated.