The best success I've had trying to quiet them has been by spraying about 10 coats of 3M Rubberized Bedliner on the inside of the Buttstock . Then filling with minimal expanding Foam . Foam alone doesn't do a thing for them . I'm not a lover of Synthetic Stocks , but they have their place . I enjoy painting them . Gravi-Gard and Bedliner gives a textured rubberized finish that is pretty rugged , and can be Painted whatever color you want .