I may have found a very good material for target back stop..

…I have been using duct seal for all of my smaller (portable targets) Home depot buckets, baking pans, etc. and today my co-worker was throwing away one of her palette plates (artist painting palette) and I stopped her and took it thinking that I could use it for a back stop. It was only around 1/4″ thick and I tested it with a 5fpe pistol at 2 yards and it stopped it cold. It barely got in an 1/8 of an inch.

I think this will be a good alternative to duct seal. I am going to take a larger tupperware dish and pour in layers (1/4″ at a time) let dry, pour another, etc. I think plain ol cheap acrylic house paint will do the trick. The question is: how thick would it need to be to stop, say, a 100 fpe 7 ring slug, and so on….