Bought this for my oldest son last summer, it worked OK for a little while but quite firing after a couple hundred rounds. It makes a nasty grinding noise. I played with the motor adjustment set screw and some times that worked, other times it doesn't. I pulled the gun apart tonight and the gear on the end of the motor looks like it's chipped and some of the gears are twisted towards the bottom of the gears. I just found the owners manual on line tonight and will pull the gear box shortly. Anyone else have this gun and experience the same issue? I'm guessing I will find more of the same in the gear box, how to I fix the problem? I found a video online for "blue printing" the gear box, but it was all about "feel". What up grades should I do while it's apart? Actually, it would be nice to pin point the problem first, what should I look for? I am a noob with AEG's, but am mechanically inclined and have tools to measure and test preload and or preload. Whats the best way to fix this thing? BTW, I just bought myself a G&G M16 pro line and my gun collector brother a PPSH wood stocked gun for X mas. The birds and squirrels are going to be in a world of hurt this spring!