in the old days (late 70s, early 80s, when I lived in Pacific Grove), Hunter Liggett would get closed fairly regularlly for a few days to a week at a time while they had live fire exercises. I knew a guy who worked as a civilian scientist contractor who was involved down there when they took apart a Russian Zsu23 to figure out why it was so effective and our really-really-expensive-and-complicated equivalent didn't work for jack (answer? Russian Zsu was really simple and relied on vacuum tube high power pulse radar and analog servo electronics, none of this fancy computerized buzzwha). They also tested the Bradley Sinking Vehicle there in that time frame (Hey, lets bolt some MORE mission requirements onto this pig, and see if it can float!)
More typically, the closures would be for a few hours, you could cue up at the gate, and eventually they'd let a caravan through lead by an MP. I took that option once and got to see a few dozen tanks traipsing across the country side 1/4 mile off the road.
Experience is what you get when you don't get what you want.