[Cokeman]

I tried to follow the posted advice as much as possible. I didn't have a new set of gears on hand. So, I cannibalized the gears from the original Aftermath gearbox (I counted the teeth, they were the same ratio as the ones from the JG mechbox).

I removed everything (except for the trigger switch) from the mechbox and placed shims until the gears spun freely (giving it a good spin - it spun for about 2 seconds). I noticed if I added any more, it would bind. So, I figured that the shim was "OK". I re-assembled the gun and test on my chrono. It shot at 380-390 fps, with a 20 rps. I fired about 120 BBs through the chrono (mainly because my chrono is temperamental and sometimes doesn't register the BBs). Then I set up a target to "stress" test the gun. After about another 100 rounds (long full-auto burst, it jammed).

So, I took it apart again. Again, everything seemed fine. This time, I slowly turned the gears and watched how everything was turning. I paid careful attention to the meshing with the teeth on the piston. That's when I noticed that it wasn't really meshing very well with the last metal teeth. Just a visual inspection showed that last metal tooth was spaced a little farther than the other teeth (see attached picture). Using a ruler, the spacing between the plastic teeth was about 3 mm. The spacing between the metal teeth and the plastic teeth was about 3.5 mm. Is this normal? Can this slightly wider spacing cause my gun to jam?

I took the piston from my Aftermath mechbox. The spacing between the metal teeth and the plastic teeth was about 3 mm. So, I used it instead. It worked fine (I was shooting full auto bursts for about 5 seconds at a time) until something broke. But, it kept working, but at a lower fps. When I took it apart, I noticed that the metal tooth had broken (bent over towards the plastic teeth), causing the piston to release prematurely stripping all of the plastic teeth (second attachment). So, now I guessI need to buy a new piston. Any recommendations for an inexpensive one?