I highly recommend the SHS gearset. Make sure it's not from the "lemon" batch though, I don't know how to tell if it is or not but the user MacieckA should be able to tell you (he also has a post somewhere about measuring things to tell if it's from the lemon batch or not)
http://www.airsoftstore.ca/index.php...r3h586ks8h67i0
Also, one more thing, don't fire your gun and turn your hop up while the bolt is locked back. Reason being is that it somehow disables your Anti Reversal Latch and can shred your gears. One of my friends found that out the hard way.