Send it to me. I'll clean all the "cosmoline" and cob webs out of it for you.
Seriously, a patch or two down the barrel with your bore cleaner of choice followed by a dry patch and you should be good to go. A through visual and function check would be a good idea too.
Note: Do not let the hammer fall on bare metal. Use your finger or a hammer block to avoid beating hell out of things
FUNCTION CHECK
Verify that hammer locks to the rear when pushed back.
Verify that hammer pivots forward when trigger is pressed.
Without releasing the trigger, push the hammer back again and verify that it locks (caught by disconnector).
Releasing the trigger should not cause the hammer to pivot fully forward (caught by trigger).
Hammer will fall when trigger is pressed.
Another oneAnd best of all:
How to make a tinker-toy collection into an AR.