Back in 2005, the U.S. Army's design for a new assault rifle, the XM8, was cancelled. But the manufacturer incorporated one of the key components of the XM8, into M4 rifles, and produced a hybrid, the HK 416. Heckler & Koch (H&K) designed the XM8, which was based on an earlier HK rifle, the G36. SOCOM is using the 416, but no one else is (except for a few police departments, and now Turkey). The XM8 had one major advantage over the M16. The XM8 (like the G36 and 416) uses a short-stroke piston system. The M16s uses gas-tube system, which results in carbon being blown back into the chamber. That leads to carbon build up, which results in jams (rounds getting stuck in the chamber, and the weapon unable to fire.). The short-stroke system also does not expose parts of the rifle to extremely hot gases (which wears out components more quickly). As a result, rifles using the short-stroke system, rather than the gas-tube, are more reliable, easier to maintain and last longer. HK developed the 416, for SOCOM, at the same time the XM8 was being evaluated by the army. SOCOM got the first 416s in 2004, a year before the army cancelled the XM8. The 416 looks like the M4, for the only thing that has changed is the gas system (that automatically extracts the cartridge after the bullet has been fired, and loads the next round.) SOCOM can buy pretty much whatever they want, the U.S. Army cannot. SOCOM listens to what its troops want, the army often doesn't. The Turks tested 9,000 of the Mehmetçik-1's (built by local firm MKE) first, and the troops liked the weapon. Production is being increased, and the transition will begin next year. The Mehmetçik-1 is your basic 8 pound, 5.56mm weapon, with mounting rails for scopes, a hand grip forward of the magazine and using 30 round magazines.