I came across this site while researching a pistol today. They test firearms and list common problems they have and how to fix them. They do pistols, revolvers, rifles, and shotguns. Pretty extensive lists but I'm sure theres plenty they've not covered yet. I just scrolled through the pistols because that's what I was interested in buying. There were several that had 7 common problems which sounds like a lot to me. Of course I doubt most don't have them all. The only pistol that that only had two potential problems was the Springfield SA-35. I've heard they were great but I'm sick of matte everything. Anyway here's the link.
Home
The Guns Advisor is my labor of love, born out of a passion for firearms and a desire to share my knowledge about Gun Problems with fellow enthusiasts like you.
gunsadvisor.com