BTW, I've seen clones (Sulun) where the gas venting doesn't work at all. I wonder how common this issue is among other clones, since the user probably wouldn't notice it - who actually checks whether the gas venting works? Usually, it doesn't cause any immediate failures, but it gradually eats away at the rear wall of the aluminum receiver, eventually destroying the gun or, under certain circumstances, causing feeding and ejection issues due to the brutal, untamed recoil when shooting more powerful shells.