If you're sighting-in, meaning you're not taking many shots anyway. Just enough to get it done. You can more than likely "get away with it" on public lands somewhere as long as you're savvy and opt to do it where you've hiked in a bit, and it's in an area you know seldom, if ever, gets anybody passing thru in there. And make sure you park your vehicle such that it is not visible from the road.
Or if that is not possible, that your vehicle is parked in a "popular" place to park but that you hike a darn long ways away from there to do your setup. So that way if green jeans passes by and sees your vehicle it's not out of the ordinary and spike their interest.
But typically, on public lands, you can't "target shoot", which is what they'd consider it. You *can* use firearms for the purposes of lawfully pursuing game though.
Weird right? It's like, OK, so how are new hunters supposed to learn how to make these shots, right?