No that one is not the Jing Gong Crunch or Latency were talking about. That M4 is gauranteed to break! I just started upgradeing a friends A&K m4 S-system that was $500 claimed 380fps with .12 and looks BA!
Alas, my friend gave money for looks and his own vanity. This thing had a spring no longer than the mech box and a cylinder with no port. Fancy chinese goo everywhere with brittle plastic for a nozzle, spring guide and piston. That means for about $150-$200 its being allowed back into his hands. (oops, forgot that he paid $65 for TBB here in town so...)
Stay away from cheap. My friend paid more than you plan to, now is shelling out $200 to perform like the Velocityarms M4 S-system My brother got for $340.
The real world of airsoft has no corners to cut, its one straight highway with $Kph instead of Kph. Right or left lane?