This replica is full metal and features moving parts and blowback to simulate firing.
 
This platform is modular and has many stocks, supressors, sights and other accessories available.
 
The M4 Carbine is a 5.56×45mm NATO, air-cooled, gas-operated, direct impingement, magazine-fed, select fire carbine.  It is essentially a lighter and shorter variant of the M16A2 assault rifle. The M4 is extensively used by the United States Armed Forces and United States Marine Corps (USMC) combat units as the primary infantry weapon and service rifle. The M4 has been adopted by over 60 countries worldwide, and has been described as "one of the defining firearms of the 21st century".