What is an expanding bullet.

A normal bullet passes through the target it is fired at
with very less energy actually spent in causing damage to the target. These bullets have
a thick layer made of brass or copper which keeps the bullet intact when it strikes the
target. An expanding bullet on the other hand is designed to cause a lot more damage.
Here the outer cover is quite weak or missing. So when the bullet is fired, on hitting
the target it penetrates a little and by then the lead which is filled in the bullet
comes out forming a mushroom shaped structure. Expanding bullets use more of the energy
they have to cause damage to the target.

The Hague
convention forbids the use of expanding bullets and makes their use a war crime, but in
the US expanding bullets are the preferred ammunition and are used by the police and
civilians alike.