Gentlemen, thanks for your support on the increased accuracy gained by increasing the stock weight on these air rifles.
My first effort was to - don't laugh! - fill the voids in the stock with sand. My thinking here was that sand is heavy, is cheap and it would be easy to fill the voids completely. But don't try this at home folks...
Results of that test showed that the increased weight certainly gave better accuracy, but the recoil shook sand out of the join between the stock and the buttpad - a sort of hydraulic shock set in and the sand tried to escape any way it could - preferably backwards over me
A second attempt was to fill the stock with lead pellets. Again, accuracy improved, but I couldn't stop the gun so-filled from rattling.
Next, I will be trying Electricians' Duct Seal. This is the stuff we sell it for use in our "Silent" Pellet Traps, so there's some to hand http://www.archerairguns.com/12-lbs-Putty-for-Silent-Pellet-Trap-p/aapeltrp12putty.htm
Duct Seal is heavy, easily molded into shape and doesn't rattle. It's also cheap and easy to obtain at Home Depot.
Maybe this will be third time lucky. Or has anyone else tried this already?
Archer Airguns Inc.
Online stores http://www.archerairguns.com