What I did to make my grips less wobbly:
Find an o-ring to put between the front sight/gasblock and the ring that holds the front parts of the gaurd. You might have to remove a screw that holds it in place, which isnt too important. if you get a nice thin one, you won't have to worry about it looking a bit off. I did this to my CA M16 and it works like a charm
EDIT: You might have to push the gas block itsel back a bit if its the grub screw style. The pin style gas block sight will be just fine with the O-ring
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How To Roll A Blunt