For factory handguns, how often during this process do you find a problem? Or do you mod all your HD handguns? Then in that case I'm going to assume the chances for something not working increases vs. a factory handgun.
I've never had an issue with functioning of any of the factory guns I own. I had small metal part on the FCG of my HK USP Compact break and disable the gun, but HK fixed it no problem. I wasn't using that HK for HD, but if I were, I would have done same testing after I got it back. No issues on my factory Glocks.
For HD guns, I don't really do any significant mods. Sites, mag release and slide release. I don't touch anything springs or action wise and replace with factory parts when they reach a certain round count. *knocking on wood* haven't had a factory part on a Glock fail.
However, for one of my Gucci glocks, I was having an occasional malfunction that I thought was a light primer strike that I assumed was attributed to the striker spring that they replace. I was noticing a misfire maybe one every 50-100 rounds. Sent it back and the gunsmith reported it was an issue with the action spring and extractor spring (and maybe something else) that resulted in not going fully back into battery, which led to the misfire that looked like a light primer strike. I think I'm at 800 flawless rounds after I got it back, so

But yeah, if I were to end up modding my HD guns more than noted above on the factory guns, I'd do same/similar testing. I generally don't mod my HD guns much. However, I have a number of shooting buddies that do and it adds all sorts of variables. Was that misfire due to a light primer strike from your striker spring? Or bad batch of ammo? Etc. They mostly do that to their competition guns, so no real "harm or foul" except embarrassment.
