I have been planning to build a foam target for 22lr use, I went to my FFL a few weeks ago and he had 3 hollow torso targets that someone gave him PERFECT!!
I taped up the bottom and lined it with newspaper to keep it from sticking, then I filled it with three cans of spray foam and let it sit. Once dry it fell right out of the mold in a perfect shape. I then wrapped it with duct tape thinking it would hold it together better.
I took him to the range and shot it with about 100 rounds of 22lr and almost no effect. Then I tried 9mm, 40, 45 and 223. It has held up very well. I have put over 500 rounds through it so far ( prob more like 1K ) and it is still like new. The only thing that has effected it is I think the heat, it has shrank a little bit.