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February 26, 2010

Initial Review: KJW M4 GBB Designed By Tanio Koba

Picture from:
Sales Link: KJW M4 GBB

The Tanio Kobayashi designed GBB M4 has been around for some time and in only limited runs. The design was picked up and is now being produced by KJWorks. Tanio Koba has been designing his own masterpieces since 1992 and is considered the grandfather to the Tokyo Marui GBB pistol design. As seen in this video uploaded some years ago the design featured no external gas reservoir as seen in many classic airsoft platforms and operates fairly much like a RS weapon.

A friend ordered this weapon from for $369.99. The packaged arrived early and I grabbed my camera and decided to film the unveil. Before we even shot the rifle he decided to put on his external furniture that he had from his previous GBB build. We found out many things this night about the weapon that I thought I would let my readers know. Note that the KJW M4 GBB has currently 300+ rifles out being used we were surprised to be in possession of a  serial'ed body.
Package Contents
  1. KJW M4 GBB (serial # KJ000080)
  2. Loading Cap + Nozzle
  3. 30rnd Mag (C7 - Canadian Style)
  4. KJW .25g BB's
  5. M4 Wrench
  6. Front Sight Tool
Initial Observations
The LE stock when fully collapsed did not sit flush with the buffer tube. The outer barrel is a single piece design. Buffer spring and weight is noticeably lighter in feel. At the end of the buffer tube is a removable cap similar if not the same as an AEG body buffer tube.

Before we could begin shooting we upgraded some of the external furniture.

External Upgrades
  • RS Magpul MOE Stock (FDE)
  • RS Magpul MOE Pistol Grip (FDE)
  • RS Magpul MOE Trigger Guard (FDE)
  • RS Magpul Rail Guards (FDE)
  • RS Magpul B.A.D. Lever
  • BUIS (FDE)
  • Replica Aimpoint
  • Opek-2 Flashlight Grip (FDE)
  • 7" Daniel Defense Free Float Rail
Install Notes:
The MOE Milspec stock had a little play on the buffer tube which was fixed by a little electrical tape on the buffer tube. Upon installing the 7" free float rail we found that the rail did not fit correctly and modifying was needed. Magpul's BAD lever fit fine, however, did not function correctly. Modifying was needed, dremel backside of install plate, to allow the lever to operate. 

Fire Test Notes:
We find that as noted on the KJW manual the magazine is broken up in 3 pieces (upper, middle, & lower). The loading nozzle will hold and load the exact number of BB's into the magazine (30rnds). Each magazine will hold enough green gas for 65 successful shots. This equates to 2.2 times you must load your BB's. 

The blowback is manageable there is a significant difference in recoil feel than in any other GBB rifle I have shot (AGM, WA, and WE). The KJW has a very light recoil and I feel that this aims to aid in the longevity and continuous operation of the M4. The bolt catch's successfully after each 30th round is shot and bolt works as it should should there be enough green gas (or propane) in each magazine.

Final Notes:
The KJW is designed to be a skirmish able gun in that it's easy to operate and learn without the worry of high wear and tear. Upon post research the KJW the external platform is TM compatible. This rifle body seems to be based of a KJW AEG body as indicated by buffer tube cap, modifying front end to accept rail, modifying BAD lever, wobble in stock, and even the "pot metal" feel of the body. The M4 is a AEG/GBB hybrid so not every part will fit perfectly.

Overall I think I would love to field this weapon and see how it runs in the long run. Without having such a hard recoil as other leaves me to believe that the gun will need much long term maintenance or replacement parts. (apart from the needed silicone lube). I would give it a buy if you looking into a skimishable milsim GBB.



Anonymous said... name is Agung n i owened a kjw m4 gbbr for 2 months (only 2 months) :/

now i have problem with broken upper receiver..
i wonder,if i want to replace this kjw m4 TK upper receiver, what brands/type will suite it well n have no further issues of tweaking etc..

I'm looking for a plug n play upper receiver for this gbbr m4 kjw..
please,i'm looking forward for some replies..
u can send me an email at

in redwolf n wgc, i notice some brands upper receiver,they are:
1. PTW by systemA ( )
2. CNC VLT MUR-1 Upper Receiver for (WA) Western Arms M4 ( )
3. G&P Magpul WA Body ( )

which one is suitable plug n play for kjw m4??

best regards n waiting for any favourably info from anyone :D

Anonymous said...

What type of modification did you have to make to get the Daniel Defense 7 inch rails to fit?? I own the KJW M4 and installed the rails without a problem (or modification).

How is it holding up, well I assume?

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