SCBair, a buddy of mine used to work at a quarry where those floor mounted 8-gauge guns were used as you describe. He told me that one time, the third shift guys had the bright idea of firing the thing with its noise reducer removed. (I guess a suppressor is legally okay for an industrial gun.) Anyhow, he reports that the resultant concussion took out most of the windows in that particular room!
Over the years he's given me a few of those shells, both the loaded
3 ounce slugs, as well as empty hulls. I've had a bit of fun "salting" various places with them. Kinda fun to let a law enforcement pal who works a bad neighborhood in on the joke; when one of his coworkers finds one or two of those empties on the sidewalk and reports to the precinct, there's a bit of excitement created by the thought that "one of the locals must be using a REALLY BIG gun now, oh my God!"
Btw, two things about this prank: 1) The cop who's in on the joke tells his coworkers before too long; 2) Heck no, my fingerprints aren't on the hulls..
