I can only speak of two of them in my own knowledge.
First was my next door neighbor and a kind-of shooting buddy. He had just bought a brand new Ruger 44 MAG, (can't remember if it was a flattop or not - prob was.as this was 1972), he and one of his workmates were reloading for it Friday after dinner (which included several Budweisers). Saturday, he came home from the range early and showed me the new Ruger, with the topstrap and the top three chambers GONE, and the barrel pointed down at a 45 degree. He said, "It kicked like the devil, and when I raised it up to cock the hammer, it wouldn't cock and I couldn't see the front sight."
He sent it back to Ruger with the three unfired rounds still in it. A week later, they sent him a brand new gun.
The other one was mine, and my fault. I had just bought a KelTec P-11 and was at the club shooting. A guy with a Ruger said he'd like to shoot it, and I wanted to try his Ruger, so we swapped and shot a magazine full. He laid it on the bench, I handed him his gun and loaded another mag for my KT. I loaded and fired the first shot and the slide retracted about half an inch, the magazine blew the nine rounds, follower, spring and floor-plate out, broke the plastic through the middle of the trigger guard, lost recoil spring and guide. The barrel opened up along each groove from chamber to muzzle. Oh. it stung, but no cuts or scratches.
Ruger guy said, "I should have told you, that last round seemed sort of weak."
Squib, stuck in barrel, of course. I ought to have checked it myself before firing, but . . . .
I sent it to Kel Tec with a letter of explanation in full. A week later it was back with their letter very nicely explaining - "The barrel, of course is unusable, so we installed a new one. The slide was jammed onto the barrel so we replaced that. Of course the plastic frame needed replacing, too, so we replaced that and the fire-control group was replaced as well. We value our customers so we included two new magazines for your trouble." What they did was simply take a new gun off the line and stamp my serial number in that new gun.
Lessons learned.