I used to teach skeet shooting at a large Southern University. Our range was also the police dept. firing range. Sometimes between classes, I would sit in bleachers they had and watch them.
When no one was there I would often go out and scrounge a few hundred empty 9mm cases. I stopped when my assistant mentioned that the PD had a contract with a reloader to pick up their used brass.
I really wish they'd go back to .45. LOL
Now I did manage to scrounge up a few thousand LC 7.62 cases a few years back when I friend and I volunteered to sweep up a police range that's used by multiple jurisdictions.
We had so much of the stuff we rented a small cement mixer to clean them up. It would have taken a month to do it in my vibratory bowl polisher. With that thing we knocked them out in a weekend and split them up.