LOL! I have fired mine quite a few times, but it was always outdoors, until my last range trip.
Well I had used up all of the 9mm I had brought along, except for the few it would take to reload my weapon. As I was packing up my gear, I noticed a box of .22 mag I had and thought about the NAA mini I keep in a pocket holster. The ammo in it was getting a bit old, and I hadn't practiced with it for a while. So I decided to shoot up all the .22 mag with me, then give it a good cleaning and some fresh ammo when I got home.
For some reason I didn't step all the way up to the firing line, before I popped off the first round between the booth walls. (The muzzle was only a few inches , maybe a foot at most behind the line) Even with hearing protection, the concusion startled me. After stepping out of my booth and seeing if anyone saw me do that, (yeah yeah, as if none of you guys have ever done that) I stepped up to the line and fired a couple more rounds. No problem. After a reload, I stepped back and set another one off. Again the concussion was pretty surprising. LOL! I hope to never have to fire it from inside a vehicle without hearing protection.