My grandfather-in-law was stationed in Italy. He went in with friends, one of which volunteered to clean his twin 50's so he could go out, as his friend was going home the next day.
So he goes to a movie, thanks his buddy and sees him off the next day. A day or so later his unit got in a fire fight, when he pulled the trigger on his 50's, nothing. He rips it apart, no firing pins!
He saw his buddy when he got home, who busted out laughing and handed him the firing pins!
I think he punched him in the head, but afterwards they laughed about it many times over the years.
Woodbury, NJ