Automatic weapon firing mechanism, cutaway illustrations. At top, the bullet in its cartridge is in the firing chamber, with a spring behind it. When fired (centre), the bullet is ejected from the barrel and the cartridge recoils (white arrow) and compresses the spring. At bottom, the cartridge is ejected upwards out of the gun, and a new bullet and cartridge moves upwards into the firing chamber, ready for the sequence to repeat. The fastest automatic weapons can fire at rates of thousands of rounds per minute.