The largest bullet appears to be a .50 caliber. Probably from a nearby WW2 training site. And given the context of that find (military), I'd guess that most of the others are .30 caliber, such as fired from any number of U.S. military rifles (e.g. 1903, 1917, 1903A3, M1, etc) or machines guns (e.g. 1917, 1919A4, or various WW2 era aircraft). Judging from your avatar, I'd guess that you are a bullet magnet or bullet collector. Good job!