Filling hollow tubes of my component racks

YES. Well , maybe. I am a dealer for Star Sound's Micro Bearings and this is a danger with them, they are exceedingly dense, much more than Atabits which I also handle. After I think about it you will probably not be able to get enough in to over damp it. I doubt if you will get enough gravel to do any good, I used cat litter for a while but abandoned it. I put 2 quarts of Micro Bearings in the target stands I use for my speakers [ one in each] and it works quite well, also have it is my Star Sound rack , I think it would work well in yours as it is very dense and heavy, think steel sand. But just start with a quart in each, they use to fill speaker stands full with it and I listened to one of them. it did "kill" the sound. Someone advised using steel blasting shot, I have never done this but it seems reasonable as the Atabits appear to be small steel shot and they work, but not as good as the Micro Bearings. I would give the gravel a pass.

Thanks Stan
I found a Mexican stone mix 1/16"-1/8" in size not really a pea gravel.

Stan what was the difference between the clay and the steel?