Why is the barrel size important for the muzzle velocity and the range?

Question

Why is the barrel size important for the muzzle velocity and the range?

In: Engineering

Answer 1

The longer the barrel, the more propellant force is applied to the projectile.

Assume a very short barrel. The bullet leaves the barrel almost soon as it fires, and the propellant force dissipates rapidly all over the place.

Now imagine a rifle barrel. The propellant force is contained along the length of the barrel and acts all the way along, pushing the bullet faster and faster until it leaves the muzzle.