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Ares M4 gearbox replacement (ZCI Shell)


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Ok, so my Ares M4 suffered terminal gearbox failure. Even though it hasn't been used a lot in its 4 years, the monkey metal used in the original shell has disintegrated around the cylinder head. I emailed Ares for prices for a new shell, came back as 73USD posted, plus customs and admin fees when it arrived no doubt. As I wanted to keep the repair as cheap as possible, coupled with my doubts the new Ares shell would survive any longer than the original, made me seek an alternative. :unsure:


The options available were:

1) to buy a standard V2 shell and swap the Ares internals into it; problem here being the Ares trigger / microswitch won't fit into a standard shell designed for standard switch parts, also the spring guide is different as the Ares box has a QD spring guide;

2) buy a complete V2 gearbox such as the ZCI or Specna Arms ones which can be had for around £50;


However Forum member ak2m4 suggested a third option; a ZCI shell which is essentially a clone of the Ares shell design, and comes with trigger, microswitch and wiring, plus spring guide. Costing £30 this seemed the best value option so one was ordered from his website with a couple of other bits. Great value and great service too!


The shell is a budget one but seems pretty well cast in fairness. The original Ares 8mm bearings and bushings dropped in fine, I had to remove a couple of the Ares shims to get the gears turning freely in the new shell. Whilst apart I fitted a new "Core" vented bearing piston head (I always fit a bearing piston head or bearing spring guide to my gearboxes to remove spring torque) and fitted the cylinder / cylinder head / piston / tappet plate / air nozzle. No fiddling about with the trigger and switch required, they're already in the new shell and deceptively simple in design, as is the selector plate and safety (which worried me slightly initially). All that was needed was to reroute the wiring as its fitted for a rear set up, but my gun needs a front wired arrangement. After a check everything was in place, and a relube, the gearbox was closed up, the spring and spring guide fitted and tested for free movement and function, as per the pic below.


The Ares pistol grip and motor were then fitted and the whole assembly tested electrically, and hey presto, all worked perfectly, safety, single shot and full auto!

I was advised by Pete (ak2m4) some minor filing may be needed; I found I did have to file a tiny amount where the hop unit locates in the front of the shell as it wasn't quite "round", and a little casting flash from on top ot the shell where the 2 halves meet, plus open the holes out slightly where the small receiver pin passes through the gearbox above the trigger but nothing else otherwise.

Time will tell how it stands up to use but I'm pleased to have fixed my M4 at fairly low cost AND been able to retain the quick release spring feature, and it still fires around the original velocity of 325FPS.


I would particularly like to thank (and plug) Forum member Pete (ak2m4) for bringing the ZCI shell to my attention, his website www.ak2m4.co.uk is full of useful parts at reasonable prices. :D

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  • 7 years later...

Interest to know how you got the selector to work as the standard ares gearbox doesn’t use a selector plate. Care to share?

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This thread is over three months old. Please be sure that your post is appropriate as it will revive this otherwise old (and possibly forgotten) topic.

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