The following series of images demonstrate how an M16 fires live fire:
A cartridge and bullet pair is automatically loaded into the chamber from the magazine below.
When the trigger is pulled, the carrier assembly (‘hammer’) is launched forward and hits the cartridge and bullet pair, causing the gunpowder contained inside the cartridge to explode.
The hammer and cartridge and bullet pair are pushed forward in unison up until the edge of the barrel, where the bullet becomes detached from the cartridge.
High-pressure gas generated from the explosion of gunpowder from the cartridge propels the bullet through and out the barrel of the gun.
Gas gets picked up into the gas port and travels backwards through the gas tube until it reaches the interior chamber of the carrier assembly.
The pressure of the gas received back in the interior chamber pushes the carrier assembly back into its default position.
By returning the carrier assembly to its default position, the spent cartridge is ejected from the chamber.