Reason behind bullets are hollow pointed

HOLLOW BULLET

Bullet is a fire arm which travels in projectile motion. Usually they carry explosives their main intention is to Penetration and Impacting. Depending upon the requirement Bullets are classified into two types

Sharp Edged Bullets (is also known as Full metal Jacket)
Hollow pointed Bullets

1=which penetrates inside the body

2=Enclosure of bullet parts

3=Gun powder

4=the rim which provides a place to grip the casing to remove it from the chamber once fired.

5=Primer ignites propellant 

Usually bullets are made of Lead and in some cases since lead is expensive it is made up of alloys. The reason why Iron is not used because it will get oxidized with water which results in rust formation.

Full Metal Jacket Bullet

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Hollow Bullet

Self Defense

Hollow Bullets are most commonly used for self defense, Since after hitting human tissue or animal tissue the bullet pointer will expand it appears like an umbrella which does extra damage to tissues and as a result blood floods.

In some areas hollow Bullets are banned due to their high damage to tissue. 

Full Metal Jacket

These type of Bullets are mostly used for firing air crafts or damaging enemy artillery.These are also used by snipers which hits long distance targets.

The disadvantage with this type of bullets are in some cases these bullets exits the victim and hits someone.

What bullets do Cops use?

Cops use hollow Bullets in order to avoid hitting other who lies behind burglar. If a hollow bullet hits a person it makes him motion less mean while he can get caught.

This is the main reason bullets are made hollow in short gun and hand guns.

Defective Bullet here can compared to sharp pointed bullet

Effective Bullet here can compared to hollow pointed bullet.