I have an m16 with aim top gearbox, echo 1 motor, and matrix metal body, with 6.03mm tbb, and some one piece hop up unit with hop up spacer. Ok, so I completely took apart my gearbox to lube and rewire it. I have watched the air nozzle move and it moves and expels air the way it is supposed to. I put the magazines into the gun, and they just are not shooting. I turned the gun upside down and took the magazine out, and there were airsoft bbs in the hop up unit, so it is not a feeding issue. With no bbs in the hop up unit, and no mag in, I looked down the hop up feeding tube and fired the gun, and saw the nozzle move how it is supposed to. I completely disassembled the hop up unit, lubed it, re-assembled it. I lubed up all the o-rings on it, and I lubed up the air nozzle. I turned the hop up all the way off, and double checked looking down the hop up unit and barrel to see if it was protruding out to much, and it was where it should be in the off position. Some how the bbs are getting stuck and refusing to fire, and I cannot figure anything out. I can only actually test the gun outside due to community laws, and I am only free to test it on weekends. Any help is greatly appreciated. Thanks!