the biggest problem with mine was that it came leaking through the barrel, i hevent even touched the internals. Azodin said to fix the cup seal, witch was in perfect shape.
However, mine may be one out of 1000. Other than that one problem everything seemed fine, i liked the twist lock feedneck, the trigger, and the electronics.
my best advice on buying this isto buy it from a local store instead of a website in case it beaks on you