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baker_Jeff January 14th, 2010 21:57

Tanio Koba / KJW M4 GBBR Basic Information and FAQ
This thread is for information on the bits, pieces, and customization options of the KJ Works Gas blowback M4.

Seeing as I have an AGM M4 myself, and access to multitudes of AGM/WA internals and externals, I will dedicate this thread to seeing what IS, and what ISN'T compatible with the KJW guns.

Obviously the internals are different, so I will be attempting to customize the externals.

Stay tuned!!


baker_Jeff January 15th, 2010 16:37


Upper Receiver: Metal
Lower Receiver: Transparent Plastic

Carry Handle: Metal
Charge Handle: Metal
Trigger: Metal
Trigger Guard: Metal
Internals: Metal
Buffer Tube: Metal
Dust Cover: Metal

Notes & Comments:

Stock: The Buffer tube appears to be Mil-Spec, but I don't have any precise measuring tools on hand to verify. It fits a Magpul MOE PTS stock perfectly.

Dust Cover: Actually stays closed, hurrah!

Foregrip: Fits MOE foregrip without issues.

baker_Jeff February 2nd, 2010 19:34

Fits the Element MOE handguard perfectly. Next I will be attempting to install a knockoff Daniel Defense RAS.

Rookie Ab February 2nd, 2010 23:31

The Socom DD lite rails go on, no problem.

baker_Jeff February 3rd, 2010 21:08

The Allan key bolt that holds the grip on is a couple sizes bigger than on my AGM. Had to borrow the right size, but unfortunately it wasn't marked so I can't comment on the proper size.

I installed a real steel Magpul MOE grip. She fits perfectly!

The threads that the bolt to hold the grip on are cut right into the plastic of the receiver, so make sure you don't overtighten and strip those threads.

Goldman February 9th, 2010 19:06

Did anyone work out what inner barrels work? and AEG outers work as well right? How about the threads on the lower? I heart it'll only accept KJW receiver extensions?

baker_Jeff February 9th, 2010 19:22

When I had mine apart I couldnt figure out how to seperate the inner/outer barrel. I compared it to an AEG outer barrel, and while there were some minor differences, they were very, very close.

I didn't want to open the package to actually test fit an AEG barrel in there, but next time I have a loose one on my hands I am definately going to try it out.


Rookie Ab February 9th, 2010 22:59

Inner AEG barrels need to be modded ,and is a little tricky ;) ,I screwed two inners before I got a system figured out.

The threads on the lower are totally different than most, for the stock tube,because they use a brass inner buffer tube and a M4 style outer that slides over.

The AEG outer barrels just need a small notch cut and a small hole drilled and taped for a set screw.

Hey Jeff,the inner and outer are held together with a small set screw,located on the top center, just in front of the flange on the outer barrel.

If you get an AEG outer for the KJ,make sure it's the deeper chambered one or the 1 cm adjustable one.Or ;) you can drill it deeper like I did,on one of mine.

Rob February 10th, 2010 01:52

Ares charging handle latch does not fit - it is much too small overall

Star trigger guard does not fit - the unit is about 1 mm too wide and the holes are too small for the KJ rolled pin to fit. modification may help, but the gaps and sharp edges left by fitting detract from the look. I'm using the standard trigger guard after trying to muscle it in (broke part of the receiver).

Ares tango down m4/m16 grip for GBB - does fit with minor modification - remove <1 mm of material from the inside of the grip to make it slip on easier. simple procedure to sand or dremel down (less than a minute with the dremel). bonus - no need to fill in a spot for the safety spring, the top is thick enough all-round.

G&P low profile gas block - fits with modification. it was tight sliding it onto the stock barrel and the KJ gas tube is about 1.5 to 2 mm larger than a standard aeg. Sand the inner portion of the block to fit on the barrel, and I elected to shave the gas tube down. alternatively you could drill out the hole in the gas block with an appropriate sized bit and a vice to hold it. some significant sanding of the corners was necessary to fit it inside a Madbull DD omega rail (issue with Madbull/G&p, not a fault of KJ)

if I could go back in time i would order this gas block as it fits the pins of the standard m4 barrel. my current set-up has the gas block being held be a grub screw and friction, its not going anywhere but it doesn't look perfect.

chronic February 21st, 2010 00:49

Aftermarket Parts
Hello All,
Can this thread also be updated for any aftermarket/replacement parts that are available for the KJW M4?

e.g. Cradle Velocity Reducer:

O ring piston

andrew321 March 5th, 2010 12:43

So there is no word on any way to get a full-style stock on these eh?

I'm looking into a new front end, stock and longer inner barrel...see how accurate and what kind of distances I can get out of it.

baker_Jeff March 5th, 2010 13:11

I'm sure it IS possible... but I can't get the damn buffer tube out. Tried an AR tool on it and it just won't budge. I'm not sure if it doesn't actually unscrew as real steel/WA/AGM does, or if mine is just super torqued on there.

Has anyone had any luck with this?


bshantz March 5th, 2010 13:46

My buffer tube is also sealed on real good, i tried reaming it off but it wont budge.
I noticed there was a screw on the bottom of the buffer tube that looks like it locks it in place but I'm not sure.

If you want a full stock then I would say just go for it, I don't see why the buffer tube would be permanent, considering its suppose to be as close to RS there is.

IMO since there aren't any different barrel lengths available from Tanio Koba the stock barrel length goes well with a collapsible stock.

I run a Carbine Crane stock, had to apply a couple strips of electrical tape to the buffer tube so the stock would be secure without wobble..

..I was told that KJW will be revealing accessories for the M4 and possibly some other things, since GBB has gotten more popular theres no question that they need to release some parts (considering most parts need to be custom fitted) or they don't actually fit.

Rookie Ab March 5th, 2010 20:59


Originally Posted by baker_Jeff (Post 1179404)
I'm sure it IS possible... but I can't get the damn buffer tube out. Tried an AR tool on it and it just won't budge. I'm not sure if it doesn't actually unscrew as real steel/WA/AGM does, or if mine is just super torqued on there.

Has anyone had any luck with this?


It does not unscrew like RS.There is a large cap at the end of the outer buffer tube that needs to be unscrewed.One of mine was loctited on so good it started to unthread from the receiver instead.There is also a set screw on the outer buffer tube that needs to be removed to seperate the outer from the brass inner buffer tube.

If you look in your manual,exploded drawing, you will see what I'm trying to say. ;)The set screw is located in the area where the stock locking pin engages the outer buffer tube.

dotty3107 March 9th, 2010 03:44

I have a question about inner barrel. What type (and what length) of tight bore 6.03mm inner barrel can be fitted with this gun? Any recommendation would be helpful.

EDIT: And some information about R.I.S. fitting would be helpful too. Thanks.

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