Unshimmed JG Gearboxes... (to shim, or not to shim)

[GI Joe]

When I got a new JG M130 gearbox for my Masada, I noticed right away that the gears were practically unshimmed and that the bushings were a little loose because of it.  This prompted me to wonder if the gearboxes in my two JG guns were in a similar state.  I went ahead and took the gearboxes out of my JG HK-416 and my JG G3-SAS just to get an idea of how loose the shims were.  These two boxes were pretty much identical to the JG M130 I had recently purchased with the exception of the weaker spring (assumed by the lower FPS) in the G3-SAS... even the cylinder hole placement was the same.  

Pressing on the bushings I could tell right away that the shim jobs (or rather lack thereof) were about as loose as the new M130 box had been.  Now I have had these guns for a while and never opened up the gearboxes despite having put a LOT of rounds through them.  I always figured I'd just use the guns until the end of their lifespan and slap in another gearbox when one died.

My question is this:  is it worth going to the trouble of re-shimming the gears on these guns?  Will I get much of a difference in longevity or has the damage already been done?

[Carrico]

Its good practice- every time i reshim a box i get better at it

[Northern Lights]

Yes I would recommend that you re-shim and re-lubricate the gears and air system. If you ever feel that you have a loose gear set like you described, re-shim it. There can be a .5mm of give but you are describing more than that. just remember to test with the box screwed shut and retest a few times to ensure you are really getting a complete revolution while minimizing slop.



Lights out

[GI Joe]

Alrighty, sounds like it's worth opening these up and doing it right.  If nothing else it'll give me a fun project for after I fix the FPS issue on my Masada.

[THEHOYT]

It's pretty much always a good idea to re-shim a gun after you buy it, ecspecially when it's JG or similar brands.