I used some accraglass to quiet a ramline stock years ago.Put in a big glob,then used an air nozzle with a long thin spout to blow bubbbles in it.
I stuffed some styrofoam in ,so the glass would only go in so far,then used the air nozzle to make a "spider web" across the inside of the buttstock.
I didnt try it on the forend with the air nozzle,but smearing glass around inside the hollow forend worked ok,but glass did add noticeable weight.

**********************
[the member formerly known as fluffy}