I haven't had a failure in the field due to rifle, ammunition or scope in 60+ years. I have failed to put a round in the chamber on occasion, kind of embarrassing to put the trigger on a coyote and just get a click, they give you a strange look before they run off. Some have been far enough away to not hear the click and I've been able to cycle the bolt and kill them. At the range I did find a loose base one time and missed a coyote due to snow in the barrel and expanding the last two inches of the barrel, cut that off and recrowned it, worked well after that.
Shotguns, that's another story, forends split, breechblock wear to the point the firing pin wouldn't reach the primer, firing pin spring that needed to be stretched before each hunt(JC Higgins bolt action 16ga).
