First off NICE!! I am elated that you are using real gunfire. Bravo man, just bravo. We are a dying breed. If I see one more silly pasted on clip art muzzle flash, often the same one for different guns in the same scene mind you, I'm going to stab my neck with a calligraphy pen.
You took far more cautionary steps than most including myself, so good on you again.
Without going into the obvious stuff about distance and pointing, the best advice I can give, if these weapons are yours, though its costly with real weapons, is to eternally dedicate the firearms being used to blankfire in perpetua. Never allow a real round anywhere near the weapon again and you'll be way ahead of the curve on safety. I mean you can always use the rifle(s) for another film right? We also chose guns that fire calibers that were a little bit "off" from what we shoot in real life to further avoid any stupid yet costly mistakes.
Some random notes from my experiences...
If you are shooting (both senses of the word) interior go with the lowest smoke rounds you can - its amazing how blackpowder can cloudcover an area. OTOH when we did full loads outside you are also getting a major upgrade in the muzzle flash - which is needed outside if your in open areas or against the sky. So weigh these things accordingly to your needs.
For some reason we got caught up in a weird 'try not to blink when you shoot' rut. This spiraled way out of control and wasted a lot of takes until we finally realized via a bit of research... everyone fucking blinks when they are firing real weapons, it's involuntary. (Not blinking during the rest of your non-gunfiring takes is the real challenge - but worth it)
Clean your guns out every night after a shoot, just like the real thing. PITA after a 12 hour day of shooting but do it.
Remember you'll be using Foley for the guns (recorded live gunfire sound, even under optimal conditions, is pretty feeble thanks to mic quality and/or compression)
When you are positive you got the take, and this includes your squibs, do one more. When we got back to editing all of the shots we thought were too over the top in the field ended up being the winners... The ones we thought were the most realistic ended up not translating as powerfully.
Take the time to get some CUT-INs of the weaponry itself, I don't mean when they're firing, but when they are being used to threaten, etc. Wasn't in the shooting script but I was glad we did when I was back in the editing room.
Again excellent job going the extra mile on this - your perceived production value will get a huge boost, worth every penny and sweat bead.
