Firearm

A machine gun was a weapon, the invention of which is often attributed to Humans. It is a form of firearm, which is a relatively primitive projectile weapon that rely on chemical explosives to propel a bullet at high velocities. In this case, the power from these explosives has been recycled in a way to allow the bullets to be fired in rapid succession.

This type of weapon was generally ineffective against such alien races including the Daleks and the Cybermen, but are effective to kill Ood and pierce Sontaran armour, if the bullets weren't influenced by the cordolaine. They were continued to be used throughout human history through to the End of the Universe.

Behind the scenes
Most machine guns used in the 2005 series, were Heckler & Koch G36s. These also appear in some episodes of Torchwood. Classic series UNIT troops are often seen using Sterling sub-machine guns or SLRs.