I had read that golf balls make good targets for 22 lr shooting.
a 223 traveling at 3000 fps hitting a golf ball with a plastic shell and foam core, really? The bullet goes through and into the sand bank..Are you really asking that question?
Yes. Are we talking 223, 22lr, or whatever someone reading this happens to have close at hand?
No more worried than when it hits the edge of a 2x4, or tree, or the ground.
I guess that is part of why I have never used any of those targets for target practice and make sure to hang my target so the bullet has a good chance of impacting the berm perpendicular to its path and not the ground at a low angle. I would be surprised if a 2X4 or tree is nearly as hard as some golf balls. Some designed for distance are pretty hard.
I've never shot bowling pins either. For much the same reason. I also check the berm directly behind my target for rocks and other debris before I shoot. If I was out west and could set up somewhere with miles of space behind the berm I would probably try some of these things out. I've seen two home ranges in Ohio with occupied structures less than 200 yards beyond the berm.
About two years ago there was a news report of a guy shooting across the highway into a building. I think it was a school that was out of session. Later, I heard what actually happened was he was shooting falling steel targets and the bullets were being deflected up at a ~45* angle or such. Probably a whole bunch went over the highway into a neighborhood landing in peoples yards/trees/attics. I'm not sure the tail end of that story is true, only that at least one bullet went over the highway into a school, but the scenario doesn't seem impossible.
In a good year, when 22lr is always on the shelf and the paychecks come steady, I'll put 5,000+ rounds down range. I'm sure many here shoot a lot more. Low percentage possibilities come into play.
I'm not saying no one should be doing it or that it is incredibly dangerous, but combined with some posts here, one of which was something like 'a round bale is sufficient back-stop for my 30-06' then after being told absolutely not, 'what if it is wet,' I think it is worth making a point of there being some risks involved.