back stop
I've built a backstop for my home range by taking old tires and stacking them, then filling the resulting column(s) with sand.
Staking out each column with a metal fence post along one inside edge seems to help stability. Sand could be bought in bulk, but what I did for easier handling was to buy damaged bags of sand at the building supply (half price) and chunk them in there. Once in a while, I chunk in another bag as needed
Three columns, arranged in a triangular shape, wide side facing shooter. Figure on 12-15 tires, 4-5 tires high per column.
That gives me about 30 inches of sand, per column, quite a bit more a center, with a rubber/belted outer. This is catching handgun rounds and .22 w/ no problem and I feel certain it would catch .223.