AZ_Win52--How much ammo you need or use depends on your style of shooting. If you are taking turns spotting and shooting with a buddy, you won't go through nearly as many rounds as if you are off by yourself doing the shooting. If you are sitting in one spot shooting from a bench in a target rich environment, you might go through more rounds than if you are walking around the prairie dog town and then stopping and shooting from the prone position for 3 to 10 shots and then moving on.
The way I hunt prairie dogs, I can't imagine shooting 500 rounds in one day. I usually have at least three rifles along, but I seldom shoot more than 75 to 100 rounds in 5 to 6 hours of prairie dog shooting. I would think you'd have a tough time shooting 500 rounds in an 8 to 10 hour day, especially if you are using only one rifle and stopping to let the barrel cool and also stopping to clean it every 50 to 75 shots. To go through that many rounds in 8 to 10 hour day of shooting, you would probably need some barrel-cooling device if you are using only one rifle, or many, many rifles.
I don't like to let the barrels on my rifles get hot. When I go shooting prairie dogs, I walk around the dog town. Stopping, setting up on a prairie dog mound with my Harris swivel notched leg 9-13" bipod and maybe shooting 3 to 10 shots, depending on whether the dogs stay up or not. I use a mirage shield on my barrel and that helps keep the hot sun off of it, but you still have to pace your shots so you don't overheat your barrel. I have attached a photo my Savage 12VLP setup. It is a .204 Ruger and sports a Leupold VX-III 6.5-20x40mm long range side focus scope.
I agree that it is better to take too many loaded rounds along than to run out of ammo. If you had something like a 17 HMR as well as a couple of centerfire rifles, I think I could go through 250 to 350 rounds in a day. Especially if I went heavy on the 17 HMR ammo.