[ybrik]

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.