Fires 5.56 NATO rounds, and uses STANAG magazines.
M4, shoots in 3-round bursts and semi-automatic
M4A1, shoots in fully automatic and semi-automatic
Shares 80% of parts with the M16.
An offshoot of the weapon is the M416, which uses a different firing mechanism.
(Searches on Wikipedia)
Squeaker: OMG, it is! AND IT LOOKS LIKE THE M16 OMG OMG OMG OMG
Bottom of the school heirachy, annoying M4s should be bullied in boys case and bitched about in girls houses, until they are properly behaved.
Sucking up to/ making friends with M4s is forbidden in their first weeks at school.