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Help needed with Battle Rifle project, specifically compatibility w/ GB and hop units.

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So I've been planning on a custom project for a while, namely a Halo Battle Rifle (H2A) I've been looking at various ways of getting parts for the internals. The body work will be a mix of ABS sheet (still trying to locate a good source that isn't extortionate) for the main structure, and 3D printed PETG for the rest. 

I've been looking around various sites at second hand guns, as well as official stores for V3 gearboxes. I considered the P90, but that required a P90 hop up which is fairly hard to find. 

The most likely solution will be an AUG (second hand CA AUG or a new gearbox), but a G36 (a JG GB) may also work. My prior experience has only been with V2s and M4 style AEGs however. 


My primary question is, how compatible are the hop ups of the G36 with the AUG GB, and vice versa? Will they both accept standard aftermarket AEG barrels / hops? This is assuming I ditch all bodywork, and the only concern is how well they seal and fit together. I noticed the two V3 gearboxes have some differences, like the odd prong on top of the G36. 


I've heard that the CA AUG internals can be a bit... sub par, and also that the gears are non standard. If I were to get a JG G36 gearbox, could the part on the top be removed? 


My final enquiry is, for those with knowledge of AUGs, would it be possible to change the trigger mechanism to a remote microswitch, and change the fire select to a standard plate? If not, any idea how to make it remote, without having the long, unwieldy and unreliable mechanical system on most AUGs?


Any help is appreciated. If you have any ideas of a good place where I can source a decent GB for fairly cheap, I'd appreciate it. For the moment I mostly just want something to build around that can be upgraded later, as the dimensions can't be found on the net, and having the physical thing to work with is much preferable. 

Thanks for your time.


(Sorry if I put this in the wrong topic, I didn't notice the tech bit lower down)

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are you completely custom building the body or just wanting to modify an existing one?


because if you're building your own body from scratch then you can mix and match gearboxes/hop units if you make sure and get the nozzle length right, you could 3-d print a block to hold the box/hop/mag together.


looking at it (spot the guy who's not that familiar with halo) but maybe getting a FAMAS to convert would be the best option for easy conversion? it's already most of the right shape, could maybe fit a short hicap (vietnam 20 rounder style) then cover the rest with your custom body?

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The problem with the FAMAS is it's not easy to get parts for it these days. A standard V3 would be a lot more upgradeable. It would also cost more as it's not very commonly available (second hand or new). I'm looking at building from scratch, so it doesn't really matter what it looks like. The nice thing about the AUG is that it comes with a 509mm barrel off the bat so I wouldn't have to immediately spend anything on that. Not sure about the FAMAS. 


Any idea where I could find info on which guns / hops have which nozzle length? 


As for the mag, I was thinking of having a fairly flat magazine, reminiscent of a sniper mag, ofc a bit bigger. I was going to cut down a high cap to the mechanical working (keeping the feed nozzle), then most likely print a hopper and body for it. Basically the mag will be on its side, with the BBs feeding down a slope into the bottom of the loop, coming out the side towards the front (may have issues making that work inserting the mag) or the top. Then feeding via a feed tube into the hop unit, which will likely be too far forward due to the mech box to have the mag feed directly. I don't have any exact drawings yet though as I don't know the dimensions of the GB. 

Cheers for the reply. 

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Augs are very odd internally. Not like any other AEG once you understand them a little.

The body of the gun acts as a guide for the gearbox. There is nothing holding the gearbox in place other than a plate at the back of the gun, and the shape of the internals. There are no screws or hard fixings.

The hop units are also free floating and have no location point other than the front of the gearbox.

As such you would need to accommodate a certain amount of the aug body to make it work. You would need to retain most of the stock section.

It's also the pressure between the hop and the gearbox that stops the takedown pin sliding out. The whole gun functions as 1 piece with only the hop spring and friction locking everything to the takedown pin.

The trigger is nothing more than a bar, and the gearbox has no selector plate. Instead, it uses 2 sets of contacts on the same gearbox trigger, and distance selects semi or auto.


The gearbox would suit your build. The 2 stage trigger and the simplicity of no selector would make it easy to modify.

The body, on the other hand, isn't suitable. There is very little you could remove without significantly upsetting the gun. The gun uses its shape to function, and with bit's cutaway it would prove very problematic.

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Thanks for the link Samurai, that's pretty extensive. Any idea what the tolerance might be length-wise? I imagine there must be some leeway since companies can get away with selling aftermarket nozzles and hop ups. 


Much appreciate the input Iceni. That's very helpful. It seems like the AUG might not be so good for me after all. I could probably fashion a body which can hold the gearbox similarly (extra work though), and something for the hop up, but I must admit that the trigger and fire selector part is problematic. I'm not an expert in electronics, so I don't know if I could make an electronic trigger for it. I also wouldn't want to be stuck with an AUG trigger if I find I don't like it :D


There was another BR project that used an AUG as a base. They however retained most of the body (for reasons you've made clear)


Looks like the G36 or AK might be my best bets. I might do some digging on G36 gearboxes, see what that bit on the top is and whether it can be removed. I've sent an email to a site called bullseye country sport asking when they'll be getting their JG complete gearboxes back in. The CYMA is also an option, but I haven't heard nearly as much in praise for them as I have for JGs G36s. 


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One option that might work using the AUG is to scrap the body altogether.

Make a peg board of just the gearbox, hop unit and inner barrel. On something solid. So you can physically clamp the hop into the gearbox and it might work.

The trick would be ensuring that all 3 sit perfectly in line. It wouldn't be easy but it should be possible.

I would scrap any notion of the gun splitting. Run with a rear entry concept. So to remove the hop and inner barrel you have to remove the gearbox.

The gearbox would have to be the AUG v3 (it's slightly different to other v3's).

To control fire selection you make a sliding trigger as opposed to a normal pivot trigger. With that, you can control the fire mode with an interference bar directly on the trigger. To control distance just make part of the bar threaded rod and use the threading to set distance. Don't bother with pivoted linkages they add slop to the trigger and it will feel disconnected.

It's quite hard to explain but possible if you spend a lot of time on it.

The advantage to going with the pegboard to hold everything true is the rest of the bodywork can bolt onto that.

The hop on an AUG runs tight to the gearbox and has a little plastic spacer that locks to the hop unit. So there is no float to account for like with other systems. Provided it's up tight and inline it's right.

You also don't need to worry about the motor as the AUG gearbox is a caged motor, and locks hard into position with screws, It needs no support, and has inbuilt motor height controls.

The basic AUG can be had cheap. €89/£75

With that you will get the gearbox, hop and barrel. So it's just a matter of stripping it and mounting it all to a frame that will fit your format.

The only issue you might have is magazines. You will have to construct a magwell and lock for whatever mags you are going to use. M4 mags would probably look the best. And the standard M4 mag catch could probably be incorporated very easily if your peg board is wide enough.

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