Since Mike works in California, he's got to deal with that state's notoriously strict gun laws. Even though his firearms have been converted to only fire blanks, he pays for a fistful of gun permits every year: "assault weapon permits, what they call Entertainment Firearms Permits ... they issue anyone these licenses, which they charge a lot of money for, which we have to pay for each year ... I carry ten different licenses, literally, to do what I do, most of which I have to renew every year."
It's kind of silly that a guy in Mike's position has to have the same permits as, say, a company that provides armed security guards. But there are bigger issues. Namely, that Actual Firearms can Actually Kill people: "Obviously, blanks are still dangerous within like, 20 feet." If that's true, then how is any war movie filmed without filling graveyards with the corpses of extras? Well, first off, "A gun is never pointed at an actor on a set, even if they're 50 feet away. It's always off angle, just as an extra safety precaution. It may look on camera ... like actors are firing at one another, but they never are. At least, not when we're there."
Mike's shop has "a couple of thousand" firearms. Most of those are period weapons, like Civil War muskets. "We've had a couple hundred people at a time equipped with weaponry; that's just the live weaponry." Hundreds of non-firing extras can be equipped with rubber fakes that look good enough on camera. But how do you stop the hundreds of people with live, loaded firearms from accidentally shooting anyone?
"We're out there in the field, my crew and I, placing everybody along with the first AD and the director, so when they land in their first spot they're going to have a mark to land on and a mark to fire at. There's no margin of error. If we're doing a big battle scene, we may have five, ten rehearsals, and we're out there in the middle of that ... making sure every one of those people that's firing a blank firing weapon is landing in a safe spot."