I figured since I just got this I might as well do a writeup of my experiences so far. I'll be putting one up for the A&K M60 later today.
hex screws, hex screws everywhere
Note: The gun in the picture has been weathered, the stock has been re-finished, and the grips have been painted to resemble bakelite. The default gun is solid black, with a light yellowish wood stock.
My first impression upon hauling it out of the box was that it was very heavy for a rifle. The body is full metal, and if it's pot metal, it's very nice pot metal. The wood as well was of a decent quality, and although a rather poor color and in need of refinishing, it feels solid and has some weight. These factors mean the whole thing weighs about ten pounds, and with the magazine (also metal) is noticeably heavier than my full-length AKS-74. I did have a problem right out of the box which was that the magazine would not lock in place. I used a steel file to grind down the locking tabs on either side of the magazine and then it worked fine. The gun is very solidly built, with no wobble in the stock, which seemed to have been a problem on the AGM one. As I did my weathering, I noticed as well that there were no brass pieces in the body, another feature of the AGM one, which leads me to believe that this is a very close clone, and not a re-brand. Out of the box, the gun shot rather hot- using the poor man's chronograph (a soda can), I estimated the FPS to be somewhere around 450 with .2s, which matches the AGM model.
It was in getting it ready to test that I noticed a major issue, which is that the compartment in the stock to hold a battery is too short for any of my 8.4V or 9.6V stick batteries. Other battery shapes wouldn't fit because the compartment is circular and too narrow. What I ended up doing was taking a 3/4" wood bit in an electric drill and using it to hollow out the back of the compartment until it reached the vertical storage compartment in the back of the stock (used in real life to hold cleaning supplies, maps, etc). This enabled me to fit a 9.6V without issue, which I think is the biggest hurdle in making the gun skirmishable.
As mentioned, the quality of the body of the gun is pretty good. Getting the gearbox out of the gun to change the spring was tricky, since many of the screws are fake and should not be removed, and as noted in the subtitle, are all hex screws. Every single screw on the body of this gun and the gearbox, except two, are hex screws, and consequently a royal pain in the ass to remove. One important note is that there is a small screw in the very back of the gun on the opposite side from the other screws which will prevent the grip piece from coming off. It's easy to miss, but could break the body if you try to force it. The gearbox itself was caked with lubricant as is typical of Chinese guns, but surprisingly was fairly well shimmed, with decent spacing between the gears and minimal play once reassembled, and metal bushings. This is a somewhat modified Ver. 2 gearbox, meaning the multitude of parts intended for M4s should work with it.
With the spring replaced with a weaker one for a more controlled ~350FPS, rate of fire was measured at 13RPS on a mostly charged 9.6V. I would expect this to rise to 14 or 15 with a fully-charged cell. Trigger response in particular is very good with very little delay, and I could see myself using semi auto extensively. The hop-up was tricky to calibrate, but once properly set (causing some jams and crazy shots in the process) I was able to consistently bullseye a target 75ft away. I'm not sure on the maximum range this gun has, but it's accurate enough to be effective at 100-125ft. With a better hop-up (again, M4-style, so many choices on the market), I'm sure it could score hits at 200ft. One thing to note is that the accuracy was worse with the original spring, so a downgrade will actually improve performance.
This isn't a bad gun by any means. It essentially feels like the AGM MP44, with a few issues corrected and other areas improved upon. I can't recommend it based solely on usability and performance, simply because it really isn't skirmishable out of the box, with a too-small battery compartment, overpowered spring, and lack of magazines available on the market. What you essentially get with the Javelin MP44 is decent M4 internals in a very nice shell. Fix up the battery compartment and spring, get some magazines, and maybe throw in a new hop-up unit and improve the externals with some weathering and restaining, and you'll have a rifle that can hold its own against other AEGs and looks damn good to boot.