Today I am looking for 2 fics. The first one I have been trying to find for a while with no luck and the second was something I didn't save because I didn't think I would want to reread it again.
Fic 1: Sam & Dean are in a motel room after a hunt. Dean is performing maintenance on the weapons that they own. Sam makes a comment about how Dean cleaned the weapons earlier in the week and that there no need to do it again so soon. Dean replies that they should perform maintenance on the weapons as often as possible. This causes Sam to become anger/annoyed and he replies that Dean does not have to do every single thing their dad said. The response Dean gives after that is something Sam was not expecting; Dean tells Sam about how a hunter they knew died on a hunt due to the fact that he did not maintain proper care with his weapons. (More specifically, John & Dean meet this other hunter to take out a nest of supernatural creatures. The gun this other hunter used backfired, fatally injuring him. John & Dean tried to clear out the rest of the nest as quickly as possible so that they could take the hunter to the hospital, but by the time they were done, it was too late; the other hunter had died.) Sam is surprised because he had not known that this hunter was dead and says so to Dean. Dean replies that this occurred when Sam was at Stanford and had cut all ties to the family.
Fic 2: Gabriel came across Sam when he was a child/teen. (Possibly acting as Sam's imaginary friend.) I think Sam told John about Gabriel at one point and John thought that Sam was mentally ill. Eventually John could not deal with Sam anymore and had Sam committed to a sanatorium [a psychiatric institute]. While Sam is institutionalized, Gabe write a letter to Sam saying that he is going to break him out; Gabriel succeeds. After the break out, Sam asks to get into contact with Dean. I think in the end, Sam was reunited with Dean.
Sorry I can't give more details but I only read the ending, not the whole fic. However, I do think that I came across the fic on LJ.
PS: If you know of any other fics dealing with gun training/maintenance, feel free to rec. However, I prefer the fics to either be gen, feature canon pairings or Destiel. (No Wincest recs, I can't stand that pairing.)