Twice a year. April and October. Knob Creek Gun Range has hosted two shoots a year for quite some time, I've been going for 15+ years or so. The Patton Museum, by the way, is about 20 minutes away, and if you use I-65, it is actually on the way in. The shoots are 3 day weekends, and include a gun show and sale as part of the $10 per day fee. You can rent machine guns during the day, and take part in pistol and rifle matches as well. It's $50, for example, to run 50 rounds of 45-70 through a real Gatling gun. They shoot cars, trucks, trailers (camper type), buses, and a lot of other stuff. The crowds are huge. I saw people buying Barrett rifles in the gun shop, and they had all sorts of guns for sale at the show, it's probably the biggest Class III gun show and sale in the World, and if you wanted to buy a Class III full auto weapon and were financially and legally eligible, you could likely find what you wanted. All sorts of stuff was for sale, including a lot of surplus stuff, and memorabilia. Ammo by the case. ANY AR-15 accessory you can dream of.
I will say that parking was a complete disaster yesterday due to the rain. If you didn't have a capable 4X4, you were best off to stay on the road and walk in. We sunk a 4x4 (diesel 4x4 trucks are useless without BIG flotation type tires, and we didn't have the tires, YET) but the Knob Creek guys pulled us out. There wasn't much the Knob Creek folks could do about parking and mud, there's only so much room, and they simply can't put down enough gravel to make room for the thousands of folks wanting in. They'd have needed enough gravel to cover 100 ACRES 10" deep. But they did what they could.