I filled the pockets in my base with steel BBs and super glue. I am sharing mine with a young child and was afraid if it gets accidentally whacked or dropped we'd end up with a disaster of BBs everywhere. So as I was adding them in the pockets I added generous layers of super glue which I just happen to have a ton of laying around. Now it's quite heavy and I don't have to worry about a huge mess if it breaks. Just make sure and keep the BBs below the top edge of the pockets, I made that mistake at first and it wouldn't fit in flush with the base. If I remember correctly, based on what was left in the container I'd estimate I used somewhere between 2000-3000 0.177 caliber BBs.
