I guess, for me, it would really depend on the gun, I have been fortunate enough to have only had 2 guns so far that have fallen into this category, only one of which was a handgun, both of which were sold off to get rid of them. For me to stop trusting a handgun, or any gun for that matter I have to have consistent issues or a complete catastrophic failure of some sort (thankfully I have never experienced the latter) my first…. I will call it an uncharacteristic lemon of a Ruger10/22, a target model. The gun was VERY accurate but it did not cycle reliable and would not extract casings properly. I did a LOT of work polishing and making sure everything was working properly and it kept malfunctioning consistently with every type of ammo from federal bulk to CCI mini mags no less than 1 malfunction, either a miss-feed or a spend casing extracted but still in the action. After working on it no less than 4 times over the course of 6 months I sold it. My 2nd bad gun was a Kel-Tec PF9. The gun seemed fine at first, I fed it WWB (which it did not like) during the 200rnd break in period during which I experienced numerous malfunctions. I then switched to the bulk Remington HP ammo which was cheap and what I was going to carry for the tie being… which it fed 50rnds of flawlessly, so I figured the malfunctions were a combination of ammo it didn’t like and the break in period. After having he gun a little better than 6 months and having shot it several more times I had had some sort of malfunction, failure to extract, failure to feed, stovepipes 1-3 times in 50-100rnds each time I had shot. I contacted Kel-Tek who sent me a new extractor and spring kit which I replaced. I shot it 2 more times and was still having issues and did not feel comfortable carrying the gun. I contacted Kel-Tec who stated that I could send it to them for repair but at that point I had lost all confidence in the gun and sold it. That is what causes me to lose trust with a gun.