Final answer:
A 40mm round consists of a projectile, a propellant charge, a primer, and a cartridge casing.
Step-by-step explanation:
The components of a 40mm round typically include the projectile, the propellant charge, the primer, and the cartridge casing.
The projectile is the element that is expelled from the round and could be various types such as high explosive, smoke or illumination.
The propellant charge is the explosive material that ignites upon firing to project the projectile through the barrel. The primer is a small charge that ignites the propellant when struck by the firing pin. Lastly, the cartridge casing houses all the other components and provides the round with structural integrity.