Mine is rattly too. On any semi-automatic rifle, any random vibrations along the barrel is asking for inconsistency.
I drew a little diagram of the contact points, pivots and freefloating pieces. The stock screw, the rear bedding surfaces, the stock latch, the bands, the female groove for the front end of one piece, etc. The ups-and-downs added up to U-shaped shims (with serifs, if you know font characteristics) inside the nose of the foreend to push up where the two top guards overlap. I also put some shims under the rear of the receiver, like bedding a Garand. I used tin snips and a scrapped stainless steel coffee cup for material.



























