When adding weight, make sure of the balance point. Usually just at/ahead of the recoil lug area.
1/2" drill bit (or bigger) to the butt stock, lead shot till you get the weight/feel you're looking for.
Best to pour it in, pack it tight (no glue) then you can remove it as needed.
Fore end? Grove cut and filled with shot and remember the balance point.
I single load so my mag wells are packed tight, (shot in a plastic bag) so the extra weight can be removed as needed.