12.7X40

12.7X40 rounds are used by the pistol. They are very powerful and take one shot to kill a foe if aimed at the foe's head. They explode when they hit which makes them deadly. They are .50 caliber. This also mean they are half an inch long. It is very powerful but weak in Halo 2. In Halo 1 and 3 it is powerful. It is a very powerful pistol bullet kind of like Smith and Wesson .500 magnum bullets. They are very powerful as well.