First AEG, Javelin M4.

[siggypoo]

As the title states, I received a Javelin M4 in a trade. It is front wired with a PEQ box, but with no battery or charger I don't know if it works. Before I get to that point though, there are some structural issues I'm hoping to have help with.
First and foremost, the upper receiver slides into the lower receiver and is held in place by the front pin. The pin slides out at a moment's notice. In the receiver there's a recess for a spring and retention pin, but it's empty. Also the receiver pin itself is smooth and has no slot or indent for a pin to lock into, so I'm wondering if the pin is wrong for this gun.
With the receiver mounted, the rear of the upper moves rather a lot. There's definitely space between the upper and lower lip that causes the upper to wobble up and down, left and right.
The cocking handle just rests in the upper receiver and is not held in place by a spring, and there is no inside ejection port cover for the cocking handle to attach to, so the piston and hopup area is exposed.
The barrel rotates a few degrees freely, and I presume (hope) tightening the barrel nut once I have a tool will fix that.
Finally (for the moment), the shoulder stock doesn't extend. And has no latch. Peering inside the latch hole it appears the stud that locks the stock into position has broken off and is jammed at an angle that prevents the stock from retracting or extending. I assume I can Dremel the protruding material out to remove the stock and replace it. The buffer tube seems fine.
So I'm hoping to find out from you guys where I can get replacement (or compatible) parts for this gun, what battery and charger I should look for, and what you might suggest for the issues I've mentioned. Especially the upper/lower receiver wobble.

[cetane]

For the takedown pins, just get a set of locking pins that use a button screw on the other side to retain it. Easier than sourcing proper pin that is self retaining along with the plunger and spring. Upper receiver wobble to the lower you can fix by building up the lip with something (tape, jb weld) to make it less. It seems you have a fixer on your hands. Just slowly source what parts you need to get it into shape to either use or sell.

(Shameless plug: I have a few new sets of locking takedown pins I can part with some if you can't find. PM if you like)

[pestobanana]

Javelin M4s are first generation APS. By far the worst AEGs ever made.

The charging handle is supposed to be attached to a mock bolt on the gearbox, as well as a spring that hooks on to the front of the shell.

In my opinion this is not a gun that is worth investing any money in to fixing.

[siggypoo]

Thanks for the heads up, guys. I've fixed the extending stock, and tightening the barrel solves the front end wiggle.
I have some JB Weld here and will build up the lip gap. Should I build up the lower receiver or the upper? Does it matter?

@cetane I've found the pins you're talking about on AliExpress. Dat shipping tho! I may take you up on your offer.

@pestobanana I've no experience with AEGs, and for all I know a battery and charger will have this thing 5x5 again. I don't know what type to get for it, or even what to look for in ASC's classifieds.
I don't doubt you saying it's likely a lost cause, but it's at least something for me to work on and learn about AEGs. It's a fun change so far. What about the gearbox and motor? Are they proprietary, or can they be upgraded or replaced easily?

[RainyEyes]

Originally Posted by siggypoo

@pestobanana I've no experience with AEGs, and for all I know a battery and charger will have this thing 5x5 again. I don't know what type to get for it, or even what to look for in ASC's classifieds.
I don't doubt you saying it's likely a lost cause, but it's at least something for me to work on and learn about AEGs. It's a fun change so far. What about the gearbox and motor? Are they proprietary, or can they be upgraded or replaced easily?

If the gearbox is exactly how pesto describes it, the receiver and the gearbox are both proprietary and will only fit v2 aps gearboxes.

Run that thing until it breaks and stop in your tracks when it does. You've already put in some elbow grease so koodos to you but after having personally dealt w/ an aps (fixed by pesto coincidentally) I vowed to stay away from that brand like the plague.

Expect that gun to break at 2k shots btw. Gearbox is awful and internals are proprietary garbagio.

[pestobanana]

The gearbox shell is proprietary, but the internals are standard V2. You can probably drop in a standard V2 gearbox.

The reason I am saying it is not worth it is that the body is such a piece of shit, the internals would have to be completely replaced to have something decent, and even then its in a garbage body. Not really worth the money or effort, especially if its missing parts for the bolt to function.

[RainyEyes]

Originally Posted by pestobanana

The gearbox shell is proprietary, but the internals are standard V2. You can probably drop in a standard V2 gearbox.

The reason I am saying it is not worth it is that the body is such a piece of shit, the internals would have to be completely replaced to have something decent, and even then its in a garbage body. Not really worth the money or effort, especially if its missing parts for the bolt to function.

Iirc the trigger and anti-reverdal latch were proprietary.

The aps m4 lower receiver was too tight for other v2 gearboxes and needed modifying to fit their v2 hybrid aps gearboxes... They weren't even compatible with their own aps aftermarket parts.

Hopefully the javelin body is better and you can out in a better gearbox...

[lurkingknight]

somehow I don't think it would be worth trying if you didn't already have the parts. There's a reason these guns were like 150 bucks.

[siggypoo]

Well I have an 11.1v battery here from a lappy my pooch destroyed (thanks Bella). I've used lappy batteries many times in my RC models to great success. It fits the buffer tube nicely so I might keep the wiring foreword in the PEQ or rerouted to the buffer. If it runs, I'll give it the old college try. If it doesn't, I'll just use it to familiarize myself with AEGs better without dumping coin into it.

[ThunderCactus]

You should probably make sure the battery can handle the draw first. Laptops draw 2-3A during operation, your gun draws 10-20+ depending on your setup.
If you hit over-current draw on that battery, you could turn that buffer tube into a pipe bomb.

Real lipo's rated for airsoft use are only ~$12. It's not worth the risk to use something not meant for the job.

[siggypoo]

Oh! I didn't know that, thanks. Out of curiosity, what is "draw" measured in? All I see on it is 11.1v and 4400mah.
If batteries are so cheap (we're going to assume even after this gun dies I'll want to use the battery in some future AEG) what sort of battery do I want to look for? I don't care about buffer or PEQ; I can readily see the gannets the wiring routes through.

[ThunderCactus]

airsoft batteries
http://www.hobbyking.com/hobbyking/s...Batteries.html

and explanation of what the numbers mean on a lipo
http://www.airsoftcanada.com/showthread.php?t=156571

[lurkingknight]

The following is not an exact representation, but enough to get the gist of it:

draw is measured in amps, like any other electrical appliance. Most guns from factory draw about 16-18 amps Some chinese junk motors draw less. It's a factor of how the motor was built and what strength magnets they use. For most people, it's kinda not necessary to get into those details. Especially for this explanation.

If your motor draws 16 amps when in constant motion with the loading it has (gear ratio and spring) You will have what's called startup draw or spiking. When the gears are pulled from a dead stop, motors will draw usually around 3x the constant draw, without proper tools it's hard to measure what exactly, but it's always safer to be on the high side of estimates.

Lipo makers list a C rating, a voltage and a maH rating. If maH is your gas tank, voltage is how fast the fuel pump goes and C is how wide the pipe is, more or less. C has more to do with the internal resistance of the cells that make up the pack.

Some makers like turnigy list a burst rating, for short periods of time, those batteries are able to output more. This is useful for airsoft, since it's safe to assume 3x the constant draw.

A rough estimate of what a battery can output is this forumla: C x ampHour= amp output. It's not exact but it gives an idea. So if your laptop batteries are 2C x 4.4 of your capacity = about 9 amps max output.

So where this becomes dangerous is that the motor will ask what it needs... always it's maximum to get moving. So if the motor is trying to pull more than the wire or battery structure can handle, it will head up or meltdown. Overdrawing lipos is dangerous because you breakdown the internal structure of the cell, once it breaks down this is where you get cells getting puffy or venting gas. Lipos vent hydrogen when they break down or are punctured, add spark = fire. Add spark in an enclosed area where there is insufficient venting = boom.

[siggypoo]

Which answers perfectly how the new Samsung batteries have been knocking planes outa the air, lol.
Thanks a lot guys. I'll check the references and see if it's worth learning on. Worst case, I can break down components to sell here. Buffer tube, RIS, rear sight, and muzzle break are pretty flippin decent.