Hi PF, I didn't know where to ask this question. About 2 months ago I learned a lot about rigid bodies and realized that an object has mechanical energy when it rotates. Hence to my mind the question "Why do bullets fired by weapon don't rotates, so that they could do a lot more damage", then a friend told me they do rotates. Now I understand why. Still, why aren't bullets made of potassium so that when they enter in contact with blood they could react with it making much more damage than a common bullet. (If it is because potassium is too ductil to enter deeply I understand). Why bullets don't contains mercury or arsenic or any strong venom so that there wouldn't be any injured? Mercury wouldn't certainly contaminates the environment, but arsenic? By the way I'm against wars and any kind of weapons. These are just questions I have.