The M4A1 is an AR_platform magazine-fed carbine chambered in 5.56x45, being a shortened version of the M16A2 rifle distinguished from the baseline M4 carbine through possessing a strengthened barrel and lack of burst-fire functionality. This tag usually implicates the presence of an automatic_weapon as the M4A1 is a specifically military-issue rifle that possesses a fully-automatic fire capability.