Ruger 45 Blackhawk..
Purchased new in '99(?)
This particular .45 Blackhawk that had two chambers that were not only bored .002-.003 off their 60 degree centers- they were also off-axis, too. The gun would keep four shots in 5" at 100 yards, and then toss two shots 14"-16" out at 2 O'Clock. It was repeatable, identifiable, and conclusively traceable to those two chambers. The grip frame also 'missed' the main frame by about .006 on one side.
I had bought the gun about a month before deer season, and I managed to kill a fat doe with it by indexing a 'good' chamber up first. Once that was done I drew a layman's blueprint of the cylinder, and included a letter asking them to fit a new one and correct the grip frame misfit. The whole works got shipped in.
It came back in exactly the same condition as I shipped it. I called and got the 'within specs' line; and after much debate I got them to say they'd take another look at it. So I shipped it back again- except this time to the front of the letter & blueprint, I stapled a copy of my sales receipt marked 'REFUND ONLY-Sender will NOT accept return shipment." They mailed the check.
I like Ruger revolvers, but my take on them is that you either get a good one or you don't. Luckily, the odds of getting a bad one are still pretty small. If you do get a bad one, you are just about SOL getting them to fix on the first try- and I don't do 'seconds'.