g&p mk18 mod 0 RIS
 

Anyone have this aeg here, just want to ask if your RIS has a bit rotational play? The lock of this ris is on the handguard cap. The handguard cap is only secured by 2 holes, one for the outer barrel, the other for gas tube. If the handguard cap is a bit loose, no matter how tight screw securing the ris, it will still have that rotational play.

Anyone here has the same case?

Try tightening the delta

Delta ring is tight. The other types of RIS is secured in the delta ring (usually with a bracket passing over the gas tube. This mk18 is secured on the handguard cap.

Found a much realistic fix. On the top half oh the RIS, there is a channel with small metal rods on both sides. These rods catches the teeth of the barrel nut. But it's not thick enough that it makes the top RIS a bit rotationally loose. I put some steel epoxy/cold weld on those rods to thicken it up. I could tell how much to fill in as there are teeth marks on the channel, then let it sit overnight prior installing it back and now my front RIS has "zero" play.

This is how RS RIS is secured by the barrel nut.