I bought a new glock 21 here about 250 rounds ago. I have been finding metal shavings after about 50 rounds. They seem to be slowing down now and I have switched to plated rounds. I was told to use them and see if it goes away. I believe I have found what is wearing. It seems to the metal guides that the slide is held on by. You can see a wear pattern in all four, on top and underneath. Is this normal so far after buying a new glock? I was told they tighten everything up due to accurancy, but hoes does that work when they tight it all up, and it wears off causing play anyways?