I use car tires filled with sand. They are not set over a post. You can staple a target to the tires with an arrow T 50 stapler, bald tires work best for the staples rather than near new tires. I have shot them for a long time with my 54 cal and several 50 cal Muzzle loaders. I also have shot them for several years with center fires from 220 swift to 300 winney mag.
If you want to recover the lead just make a screen frame for 1/4 inch screen. place some sand in it and shake till only thing left is stones and lead.

Al