I have to say, with regards to rimfire and OOBs, it happens.
I have had one in a service rifle I was using (SLR) in 7.62 in the late 80s, with a Heckler Koch conversion kit down to .22..
Blew the side out of the rifle and basically trashed it be beyond repair, much to the dismay of the armourer on duty.
Fast forward to last year or so and watching the very funny Doomsday Preppers on Discovery Channel and one of the guys there, who was demonstrating how he and his son practice takedown drills with a .22, as a point to note a Ruger 10-22,
He very successfully managed to blow the end of his thumb off with his OOB,
That was ON Camera and Broadcast for all to see,
Though I guess it wouldn't warrant a withdrawal of the 10-22 from use, as it had NOT been worked on by an, and I use this word loosely, "Instructor " so I guess it failed to qualify for Appleseed attention.
OOBs happen. FTF happen. FTE happen. It's part of the cycle of using 22s. For crying out loud. Appleseed, accept it and move on!!
Rob.