So the m4 body is honestly one I had laying around, same with gearbox and internals, wiring is a bit weird since it goes up front the front into the upper section where the battery is housed.
As far as the rest of the parts, the rear cap, top compartment, and front grip it's all parts that I actually designed in cad and built out;) I'm thinking about offering a kit for sale but I'm going to do some slight revisions to make it a bit easier to handle an 11.1v and a little more room for the front wiring. But pretty minor revisions.
Design wise I like the Ares style and I grabbed some ideas off of their stuff, but I didn't dig their weird receiver so I wanted a standard one. And it was a bit longer than this build from memory, since I was shooting for as short as possible. Really I always wanted a full size AEG backup for running in winter with my sniper rifles so this was an attempt at that. Whether or not it will work in that role I don't know yet;) But it was fun to design and build either way;) And I do believe it would be a very handy in vehicle gun which I drive when I host out here, so it's surely going to see some use in that role. Though I've gotta design a kydex holster for it, right now it's setup for a sling but that's not really necessary a holster will do fine I think for this size of gun.
Luke
EDIT I attached a cross section analysis view from Fusion to show the internal setup of the end. Also the end cap is threaded, so it could be replaced with a suppressor. But since short was the plan I haven't built out that yet. Though I'll be getting on that eventually.