I have a classic mess in my shop , just now. I was shocked , when I removed the lock bolts from the side plate. The internals were a mass of rust ,though the owner says , he fired the 30 yr. old expensive custom longrifle once , a week ago. The complaint was , now the lock won't stay at full cock position.
I disassembled , and power wire brushed and polished each lock part , The only parts not rusted , were the fly , the mainspring , and hammer. Lubrication ,reassembly , and testing of the lock , was successful , but the flint was too long , and was replaced.
The lock mortise was charred black , denoting the wood stock had shrunk ,and the precision flint lock inlet , needed to be inlet slightly deeper to allow the lock plate bolster , to fit tightly against the barrel , sealing the hot ignition gasses , away from the wood in the lock mortise. The single trigger has no free play when the lock is at full cock , and when the rifle butt is bumped om the floor , the lock fires. This condition is obviously unacceptable and dangerous. I was called away , and cant work on the rifle , just now. I will check the clearance of the sear arm in it's inlet hole , and unpin the single trigger, and remove just enough wood to allow the trigger a small amount of free play , so the lock can be safely cocked completely with a small free play in the trigger motion. All should work , OK.
Will tutor the owner on proper lock maintenance , and cleaning procedure , though I doubt it will do any good. .....................oldwood