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Inokatsu M4 GBB
  • Manufacturer 
  • Model 
     M4 GBB
  • Capacity 
  • Weight 
  • Power 
  • Power Source 
     Top Gas, Red Gas, CO2
  • Blowback 
  • Hop-up 
  • Shooting Mode 
     Semi, Full Auto
  • Construction 
     Fiber Reinforced Steel


  • Excellent Blowback Action

  • Exact 1:1 size of the real steel M4 Carbine!

  • Based upon the WA M4's GBB system

  • Easy to Disassemble, with self-retaining pins

  • Able to use CO2


  • Cool down during extended bursts

  • Requires the greasing of internals regularly due to full metal internals

  • Must use Top Gas or more powerful sources

  • Does not come with a magazine

  • Very hefty price


    Although the price tag is a bit hefty compared to the WA, or the WE M4 GBBs, the INOKATSU is well worth it if you want a high-powered skirmish capable Gas Blowback Rifle. Not only are the externals exquisite with a 1:1 size to the real steel M4 Carbine, the internals needs little to no modifications for the INOKATSU to work its wonders.



    Although the concept of a gas blowback rifle isn't entirely new, the recent entry of the Western Arms Gas Blowback M4s has caused a new spurt of excitement in the world of Airsoft. As such, other manufacturers like WE, and INOKATSU have also jumped on to the GBB bandwagon, creating their own M4 (plus variants) gas blowback guns. It all started last year with the magnificent magna blowback Western Arms gun, which shook us (quite literally), leaving us wanting more. And that's what we got! We have seen Inokatsu & WE follow suit with their own GBB M4, and very recently, Socomgear and G&P have showed us their own creations. So how does it fair amongst the ever growing crowd of gas blowback M4 guns?

    Those who have been in the sport for a long time will remember the Kokusai Crimebuster as well as the Tanio Koba 10/22. More recently, Marushin has released a series of 8mm blowback models. As nicely made as the Marushin blowback rifles are, their WWII appearance puts them in a niche market, and the caliber doesn't help breaking into the mainstream either. There are also gas blowback rifles and submachine guns with external gas, such as the Escort MP5. While external rigs are much less restricting than their reputation - which can be hidden in the gear quite nicely - there is still a definite demand for having everything inside the weapon.

    Inokatsu comprises of a talented team of engineers that had previously worked behind the scenes as GUARDER's supplier of authentic conversion kits, like the famous GUARDER AKM, AK74, and various other full steel kits. When they started introducing their products under what we now know as the Inokatsu name, we got to appreciate the skills they have as engineers. The kits they produced were no less than sublime, with an insanely high level quality of construction. If you have ever seen or touched one of their kits, you will know and appreciate how solid they are. After getting some conversion kits out, Inokatsu dabbled in producing complete guns, making some very pretty-looking AEGs. Although, it could be said that this gas blowback M4 is the gun that is really going to get Inokatsu noticed.

    The weapon is well packaged with cut-cardboard pieces, ensuring that you'll receive your M4 in pristine condition.
    The internals have been modified to fit into the smaller body, with a steel CNC milled hammer and a stronger hammer spring to take the much more powerful CO2.


    If you know how to field strip a real steel M4 Carbine, then you'd know how to strip the Inokatsu M4. As it's modeled on the real thing, everything will feel right at home. You begin by removing the magazine and clearing the chamber. Push out the takedown pin until it's caught by its detent, and tilt the weapon open; the pivot pin acts as a hinge. Pull out the charging handle and bolt carrier a couple of inches, and then pull the bolt carrier out alone. This is enough for regular cleaning. The pivot pin can also be pushed out to disassemble the short carbine into even shorter components for ease of transportation in a smaller pack or even an attache case. As usual, the RIS is unlocked by pulling back on the delta ring, and the sliding stock can be removed by pulling down on the lever while sliding the stock back.


    After taking it apart, what greets you is a familiar sight (assuming that you're lucky enough to have a WA already), as the
internal workings are the same as the WA M4, with the crucial difference being that all the internals are replaced with Steel parts. Things are stronger and heavier. To combat the heavier bolt, a stronger 150% recoil spring has been fitted with an Aluminum Recoil-Spring Guide. Essentially, that means that the Inokatsu is built to be capable of using much stronger gas and of realising a much higher velocity than the WA M4. But of course, that means that requires more power to get it working optimally. Whilst the INOKATSU M4 is able to use the WA's Magazines, Top Gas just doesn't seem to cut the mustard due to the much heavier bolt and spring set. It functions best only when using Red Gas or from more powerful sources such as CO2. As it was designed to be capable of using CO2, INOKATSU themselves will be releasing their CO2 compatible magazines soon.

    The bolt carrier is constructed completely of heavy duty steel, whilst the bolt itself is constructed out of high grade Aluminum making the system extremely robust.
    The hop-up chamber is constructed from aluminum with an enhanced hop-up rubber, making the INOKATSU M4 that much more durable.


    As we mentioned already, the kits that Inokatsu have made previously were prime examples of what is possible in the manufacturing of metal bodies for airsoft guns. The Inokatsu M4 is no different, showing-off a quite simply beautiful exterior that mimics the real steel.

    The entire exterior is made from forged-aluminum, with the exception of the Fiber-Reinforced Polymer (FRP) grips and stock. Whereas the WA M4's body was modeled after the old-type MGC M4 bodies, the Inokatsu M4 SOPMOD's body is modeled after the real steel M4, thus is built to a 1:1 scale of the real-steel counterpart. So, it not only looks ultra-authentic, but it also feels it too. Look on the sides of the main receiver and one can see that the markings have been delicately engraved, and there has obviously been a lot of attention paid on maintaining a sense of authenticity.

    The front set itself is a full length Inokatsu RASM Real Type M4 RAS, featuring authentic markings from KAC, and it comes standard with 4 rail covers. Much like other parts of this gun, it is also made of steel. The entire front kit feels extremely sturdy, and is not only great to look at but also provides a great platform for adding your favorite accessories!

    Thanks to the 1:1 dimensions, the scope for adding accessories is slightly different to your average AEG. As typical AEGs have to have certain external parts different from the real steel to provide room for the slightly bulky internal parts, such as the motor and gear box; which means that your ordinary after-market AEG grips won't fit on the Inokatsu. However, because of the real steel dimensions, it is possible to add certain real steel accessories to this Inokatsu as well as select aftermarket AEG stocks.

    When the WA M4 first came out, there were a lot of gamers wondering and anticipating when the after-market metal bodies would become available for it. It certainly didn't take long for them to make their way onto the market, but Inokatsu have created a stunning-looking steel piece that comes fitted with all-steel internals with a forged-aluminum body out-of-the-box. Holding it feels good, with an ample weight and a solid construction that makes it feel like it was made to last. There's no denying that even from their days of creating kits for Guarder, through to their conversion kits that were released under their own name, they have built up an expertise in creating these stunning metal bodies made from materials such as steel. Of course, even their kits were not what you would call cheap, but it is true that you get what you pay for. With this gun, you certainly can see what you get for your money, and those solid "clinks" and "clanks" when you pull/push/rotate those levers/pins/switches are sheer joy to the ears. Looking at their metal bodies, you can appreciate the sturdiness of it all, especially due to the use of steel in the construction. Those cheaper, pot-metal bodies don't even compare. There are other brands on the market that make excellent quality metal bodies for their standard guns (such as Real Sword), but in terms of gas blowback rifles, Inokatsu are really leading the way. Western Arms' offering obviously comes with a plastic body as standard, and the recent gas blowback M4 from WE does feature a full metal body, but quite simply not in the same class as the steel Inokatsu.

    The full aluminum KAC RAS unit even has laser etched original manufacturer markings on the underside!
    The markings are all engraved with precision into the metal body realistically, with each INOKATSU M4 SOPMOD featuring its own unique serial number.


It is quite important to note that this Inokatsu M4 does NOT ship with a magazine - you will need to buy a magazine for it. Thankfully, the INOKATSU supports the use of the WA M4 magazines, as well as its upcoming CO2 M4 GBB mags. As of writing, only the WA M4 magazine is available, thus there isn't much choice in the way of magazines. The WA magazine is heavy and feels realistic, being as it's all metal made with a dull gray finish. The fill valve is located in the rear of the magazine instead of on the bottom where dirt would tend to get into during a skirmish; the magazine holds 50 rounds, feeds every one of them and locks the bolt carrier back after the final round.

    While the magazine can shoot all the BBs out and locked back reliably when shot in semi and short bursts, a continuous burst of 50 rounds cooled down the magazine to the point that the pressure was not sufficient to propel the bolt carrier all the way to lock-back. The bolt hold-open feature can be disabled, so you can shoot the weapon without BBs to show off the blowback system to your friends.

    It's all steel! The materials used for this M4 are second to none.
    5 position stock.

    Performance and Recommendations

    The Inokatsu bolt carrier is made from steel, which is much heavier than the WA M4 one, giving this gun a shoulder-shakingly hard blowback. As was noted this, teamed with the 150% stock spring, means that it requires stronger stuff to power this gun. You can forget about using the HFC134a gas! We would definitely recommend using Red Gas to reap the rewards of the Inokatsu's excellent blowback system. Top gas can be used, but doesn't feel sufficient really. If for some reason you don't want to use Red Gas, then you could change the steel bolt for a lighter aluminum one, along with downgrading the stock 150% spring to a 120% one.

    At 20 degrees C, the Inokatsu M4's initial muzzle velocity reaches a tasty 400fps with red gas but due to the cooling issues of the magazines, the Inokatsu suffers the same problems to that of the WA, and WE M4 GBB rifles; where the cooler the ambient temperature and the more you fire from the same magazine, the less power you would get out of the magazine. A simple tried and true remedy for this is to store your mags together with a heater pack to keep the mags nice and warm before use!

    Because of the forged-aluminum external and steel internal construction of the Inokatsu M4 GBB, the first thing that needs to be done upon taking the Inokatsu M4 out of its nice packing, is to field strip it, and clean everything inside, and coat them all with a very generous helping of silicon grease (yes, grease, not spray-on oil). Once you have completed these steps, put your Inokatsu back together and fire a couple of mags through the system to make sure everything is running smoothly, and you're all ready to go!

    The recoil and sound of this carbine is so intense that we haven't seen anyone shoot this and not smile after the first shot. Even though a standard AEG has much more ammo capacity than a M4 GBB for a skirmish, the Inokatsu M4 emulates the real steel firing experience giving you that much more satisfaction when you achieve a "kill" in game! The advent of reliable GBB rifles won't wipe AEGs out of existence, but finally the realism-minded people have a skirmish-able option that suits their needs.


    Inokatsu has come a long way from their humble beginnings of producing full steel kits for the AK series AEGs, to today; producing the heavy duty 1:1 scaled M4 GBBs. With a forged-aluminum body and steel internals, exquisite engravings on the body, coupled with its skirmish-able qualities, the Inokatsu M4 GBB has opened up a whole new frontier in developing heavy duty Airsoft GBBs.

    With all so many companies having jumped on the Carbine GBB bandwagon and with (we're sure) more to follow, Inokatsu surely face a lot of stiff competition from rival companies. However, we think that with their M4 gas blowback, they have succeeded in producing a gun that is sure to give its competitors a run for its money. With the combination of a full steel body with 1:1 size of the real steel M4 Carbine, the Inokatsu M4 GBB is well worth owning for both collectors and the serious skirmisher.