The danger from live small arms ammunition is very low. Assuming that you find an unused cartridge or shell and the primer and powder is still good, the primer would have to be hit very precisely to ignite the powder. What follows is that the gasses from the burning powder will push the projectile out of the cartridge or shell and harmlessly fall to the ground. Because the gasses are not contained by a gun's chamber and barrel there is nothing to push the projectile. In a gun, the gasses produced by the burning powder expand quickly under pressure pushing the projectile faster and faster down and out of the barrel. I have found numerous unfired cartridges while detecting and most of them show evidence of where the gun's hammer had struck the primer and it didn't fire, so were discarded. I have also found perfectly good cartridges that were evidently lost. I once found a large military shell that I left "as is" and reported it's location. What really scared me was when I found a buried box of TNT with blasting caps. The blasting caps were detected and as I uncovered the box and realized what it was, I almost s..t myself. When found, what you do with explosives or live ammunition is up to you, like rattlesnakes, I tend to leave them alone.