Diagram: Firing a Rapid Fire Weapon — if the firer remains stationary it can fire 2 shots at targets up to 12", or 1 shot up to the weapon's maximum range. If the firer moves, it can fire only 1 shot, and only at targets up to 12" away.
Self-loading weapons that carry a reasonably large amount of ammunition are called rapid fire weapons. These are very common and usually come in the form of sub-machine guns or assault rifles. They can lay down a withering hail of fire, especially at close range if the firer is stationary and concentrates on aiming and firing. Their high rate of fire also means they can be fired effectively 'from the hip' when a squad is advancing, spraying shots into the enemy whenever they present themselves.
If a unit armed with rapid fire weapons moves, each model can shoot once at targets up to 12" away.
If a unit armed with rapid fire weapons remains stationary each model can shoot twice at targets up to 12" away or once at targets over 12" away.