[Flat Six]

Lots of good suggestions; I'll add two for those 'just in case' moments (outdoor ranges, obviously):

1) Program the range/RSO number into your phone so it's easy to call when something goes wrong
2) When you call 9-1-1 specify that there's been a 'training accident' and you need immediate medical response -- you don't want to say 'shooting' or 'someone got shot' else the dispatcher may interpret as an active shooter scenario and send 5-0 (unless, of course, that's what happened)