I bent the heck out of the gas tube on my Russian refurb, I mean really bent, like curved :/ . fired 100 rnds straight pull for the rest of the day. Went home and patiently straightened the tube by eye with screwdrivers and 2X4s. Took it out, test fired, shot another 200 rounds semi-auto, no problems. I thought it would need a new tube, - it has remnants of 2 other serial numbers on that tube too yet, to boot.
I've only shot corrosive, always clean it meticulously, never have taken the bolt apart in well over 1000 rounds. Only small issue aside from me bending the tube - which has nothing to do with design of the rifle, is that some of the pressed in pins on the barrel/reciever have loosened and it became loose in its laminate stock after around 400 rounds.