Some do but many don't feature a grub screw, so you need to tighten it down properly (some guns, like WE, addressed this by putting an o-ring behind peel washer; TM use to put a small spring behind it, which wasn't very effective. You might want to use a lock washer or threadlock).
That's for any airsoft FH, not just Chinese. Honestly I rarely see grub screws on them anymore.
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