Yes...(on the bolt..) once, years ago, I had a brand new Rem 788, found filings and crud inside the bolt. Another time I used a friends Rem. 721 and it failed in november's deer season.. I found that he always oiled the rifle, and put it away.. over the years the oil got cruddy, and it would fire in warm weather, but failed in the cold.. Since then I always take a newly aquired rifle, either disassemble the bolt, or ( in the case of one that I don't care to dissasemble..like a semi auto) strip it down to the metal, and soak it in a pan of old gasoline, and blow it out with a air hose blower, then only use a light synth. oil for storage. Like I said previoulsly, I cleaned and de-oiled all of them in the test. I just picked up a used vanguard that had crud down inside the bolt housing, it didn't seem to affect the fall of the pin... but its clean now.