I hope you have found an answer by now, but in case you didnt I can tell you what I did. I have a Savage LRH in 300 WM in which the factory muzzle brake does little so like you I wanted to add weight so I bought 1lb of lead fishing weights and filled the butt stock using Great Stuff foam to hold it all in and keep it from rattling. FYI if you use this method do a little at a time because you will end up creating a chamber in the foremost end of the butt stock near the grip which keeps the foam from setting up. I found this out the hard way after 2 months of having added the weight I went shooting removed the cross bolts for the cheak piece and within a few minutes foam started oosing out. So again do it little by little squirt a little foam in drop in the weights, let it set up and repeat until done.
