The four components of a round of artillery ammunition. 

1. the fuse

2. the projectile 

3. the propellant

4. the primer

1. Fuses are the devices that trigger the artillery ammunition. 

2. The projectile is the munition or the "bullet" fired downrange.

3. The propellant propels the projectile to the target.

4. Upon being struck with a huge force, a primer reacts chemically to produce heat, which ignites the propellant and fires the projectile. 

Artillery Ammunition:
The first documented record of artillery with gunpowder propellant used on the battlefield was on January 28, 1182. General Han Shizhong of the song dynasty used escalade and Huochong to capture a city in Fujian. These vase like cannons were initially cast in iron or bronze around a core.

A round of artillery ammunition comprises of four components:
1. the fuse 
2. the projectile
3. the propellant 
4. the primer