I have a 1950's vintage .22 cal Remington 512 (passed from Dad) that sometime fires when the bolt handle is "closed". It doesn't happen all the time; and sometime it drops the firing pin on the back of the bolt without firing the round. About 75% of the time it works as "advertised", but goes off unexpectedly for no "found" reason. I took the rifle to a gunsmith several months ago to have it "relined" and to have the trigger "fixed"; the new liner returned the rifle back to its original accuracy level, but they were unable to fix the "haphazard" and dangerous trigger malfunctions. I can preclude this "unsafe" condition by putting the gun's "safety" on before opening the bolt and "cocking" it. I have looked at all three (3) versions of this Remington (rifle) "rim fire" to include the "clip" and "single shot" versions (this one's a "tube fed" model) and they all are have similar trigger mechanisms, but with different trigger/sear parts listed. Any help will be appreciated! On last resort, I will attempt to purchase a new trigger assembly, if available. Thanks, Kaiser