The bullet enters the
barrel, which is has grooves (called
rifling) which adds a spin to the
bullet as it is propelled through the
barrel. This increases the accuracy of the
shot.
The
force of the gas pushing the bullet
forward, also pushes the rest of the
firearm back (Newton's third law of
motion) causing
recoil. The sudden
release of pressure as the bullet exits
the barrel also causes a shockwave of
sound as well as the
muzzle flash
as the burning powder escapes the barrel.
The caliber of a bullet is
the diameter of the bullet in the casing
and can be measured in metric (9 mm) or
empirical (.45 caliber). The caliber also
can imply the stopping power and amount of
recoil that the ammunition will have.
