If a bullet is fired into the air it will travel a certain height and lateral distance (depending on its caliburand the angle at which it was fired) and it will then proceed to fall. When it reaches the height above the ground it will have the same velocity as when it was fired. So if you were unlucky enough to be in the path of a falling bullet and it would hit a major artery, for example, then yes it would kill you. However not many people actually fire bullets into the air so not many are flyong aroung in the atmosphere.

Just an addition to Farino's answer - if you throw a feather into the air very fast, it gets to the top of it's trajectory then almost immediately "floats" downward at its (slow) terminal velocity, and will never hit the ground (or the point where it left your hand) as fast as you threw it up. A bullet is the same - it would still fall very fast, but would not fall as fast as the muzzle velocity of the weapon unless you fired it in a vacuum (on the moon maybe??). Terminal velocity of a 30 cal bullet is 91 m/s according to http://www.loadammo.com/Topics/March01.htm but the muzzle velocity on firing was 823 m/s. This is a significant drop in the energy of the bullet to 40 Nm of torque, whilst the army suggests 80 Nm is required to create a "disabling" wound. Thus, although it would seriously injure you, it *hopefully* wouldn't kill you! Two asides: 1. The bullet took 49 seconds to get back to earth (so you've got time to hide!!), 18s up and 31s down. 2. Out of 500 shots fired from a fixed gun adjusted perfectly only 4 bullets actually dropped on a ten foot square area - you'd never hit yourself if you fired from a gun you were holding... unless you were really unlucky... Hope this helps.

The MythBusters on the Discovery Channel tackled this one during the past season. What they discovered is that it depends on the angle at which the bullet is fired. If it is fired straight up, then it will loose all of its moment at the top of its journey. As it begins to fall back down it will then begin to tumble and its speed will be limited by friction with the air. Thus, the speed at which it will fall will be limited to terminal velocity. The terminal velocity for a falling, tumbling bullet is not high enough to cause serious injury. However, if the bullet is fired at any angle other then straight up, then it will travel in a ballistic path. This will result in two things occurring. First of all, not all of the bullet's kinetic energy will be expended fighting against gravity. Second, the bullet maintains its stability and does not start to tumble. These two factors mean that the bullet will come back down at a much higher velocity than it would if it were fired straight up. The further from straight up the bullet is fired, the more dangerous it will be when it comes back down. So, bottom line, it is nearly impossible for someone to hold a gun perfectly straight up while firing it. (The MythBusters built a special holder for their guns when they did the experiment.) So, don't go firing a gun into the air because you could very well hurt someone.

I cant say for certain yes or no. However if a bullet is fired straight up in the air then we have the equation f=ma so for a bullet that has a mass of 1kg which is 2.2pounds then the return force will be 9.81N since the accelaration is due to gravity which is 9.81m/s. However when studying projectiles you see that an object has maximum range an velocity if it is fire at around 45 degrees so with this the force will be greater but probably with a heavier bullet something can happen.

Gravity does that, however the momentum is reduced and eventually it's TOO harmful!

i think it can kill someone since theyre bullets