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Being part of a small team that has been playing exclusively with GHK AK series guns over the last years and maintaining these guns, I’ve become quite familiar with the platform, its parts market and upgradability as well as typical issues a GHK AK user might run into. Since I’m still noticing a lot of technical questions coming up regarding the platform in other threads, I thought I might as well take a couple moments to write up a couple words and provide an overview over GHK’s AK system.
Now, I’m aware that some of what I’m writing here will seem rather obvious to some of you and other things might not be described in enough detail. What I'm trying to do is to build a more or less complete guide to the platform. I guess it goes without saying that noone is ever going to read this entire wall of text in one go; the guide is intended as a place to look up solutions and news regarding the GHK AK. Naturally, I won’t be able to think of everything in the couple hours I’m taking to do the initial write-up, so I’ll try to keep this post updated. Please tell me if you find that the guide leaves a question unanswered or an important note or product unmentioned. 
Right now, the guide is lacking pictures to make a lot of the instructions more understandable, and I will hopefully soon find the time to take those. Of course, everyone is more than welcome to contribute. ; )

As there are plenty of reviews around, I will skip an introduction of the gun and get directly down to business: You’ve bought a GHK AK - what now?

Upon receiving your GHK AK, there are a couple checks and initial modifications you can do to it to avoid issues down the road:
  • Taking care of misfeeds #1: One of the most common issues with GHK’s AK platform is misfeeds caused by the feeding lips of the magazines being too tight. This is usually only the case using 7.62x39 magazines, but can also occur with the type 74 5.45x39mm versions. Due to overly tight feeding lips, BBs tend to “jump” out of the magazine when hit by the nozzle and thus end up somewhere between the bolt and the front wall of the receiver or hop-up unit instead of smoothly running up the loading ramp, resulting in a jam.
    This can be remedied by taking a roundish needle file and taking a tiny bit off the inside of the feeding lips in the forward direction. It is advisable that you take off the bottom plate of the magazine, undo the screw connecting the magazine shell and body and slightly slide out the magazine body so you can hold down the follower while filing down the lips. Keep filing until you can manually press a BB into the magazine without the use of excessive force. Do not take away too much material though, as the BBs being able to just roll out of the magazine on their own can result in double-feeds and jams. Try to take away equal amounts of material on both lips so that the BB properly aligns with the loading ramp infront of the hop-up unit.
    If you’ve already experienced jams before doing this mod, make sure to remove any residues of crushed BBs from your hop-up unit and nozzle.
    In case you’ve taken away too much material and are now experiencing double feeds, you can install a new set by sliding the magazine body out of the shell, driving out the two small pins holding the lips to the shell, applying some silicon oil to the packing on the new feeding lips and replacing the old ones with those. Make sure that the plastic lever on the left side of the magazine is properly seated on the pin and in the BB channel before putting everything back together.
  • Taking care of misfeeds #2: In case you’re still experiencing misfeeds after filing down your magazines’ feeding lips, another mod you can do that helps in that regard is removing your hop-up unit from the gun and filing a round groove in the bottom of the unit that is equally wide as the gap in the loading ramp. To understand what I’m talking about, take your hop-up unit, attach the loading ramp to it (while the unit is out of the gun) and then try to roll a BB up the loading ramp into the unit. You will notice that the BB will actually bump against the hop-up unit and cannot by chambered smoothly. Take your needle file or dremel (depending on whether you’re working with a plastic or metal hop-up unit) and then proceed to making a roundish cutout. Most likely, the groove won’t need to be more than 2mm deep at its deepest point in the center for the BB to properly feed, so take it slowly and keep testing with a BB.
    Some GHK AK owners actually also cut away a tiny portion of the hop-up rubber in the same spot, but I haven’t found this to be necessary. However, using a hop-up rubber that has a shorter but thicker lip rather than a longer and thinner one certainly helps. Check the parts section of this article for recommendations.
  • Checking your magazines’ seals: While GHK magazines usually arrive in leak-free condition, they can start to leak after continued use. Sealing them isn’t necessarily something you’ll have to do upon receiving your gun, but at least in my case it was a task I had to do once and never again, as my magazines are still holding their gas three years after I sealed them. Thankfully, since the magazines are nicely designed and utilize cylindrical gas containers (instead of holding the gas directly in the magazine body like the first generation WE magazines), sealing them is also an easy task.
    There are two common approaches: Samoon suggests to just take off the bottom plate of your magazine, remove the screw holding the shell on the magazine’s internals and then unscrew the cylindrical gas containers (and their caps) to apply silicon oil to all the O-rings sitting on the threads. While you’re at it, make sure that none of the O-rings is busted/torn and replace them if needed. In addition, you can use a valve key (or similar tool) to remove the fill-valve and output-valve to make sure those are also well oiled. Be careful screwing the fill-valve back in, as it can break if you try to tighten them to forcefully. In case you’re using CO2 magazines, the process is pretty much the same, but instead of a second cylinder and a fill-valve you have an O-ring beneath the cartridge piercer to seal, although it’s quite rare for the magazines to leak through this seal and I have not done anything to it on all of my magazines.
    Another approach some of the folks at gasguns.info and myself have taken is to actually put some Locitite thread sealant (or similar) on the threads of the cylindrical containers in addition to the O-rings.
  • Ensuring the gun is cycling smoothly: Like every GBBR, the GHK AK requires a break-in period before it runs completely smoothly. You can make sure your gun is running as smoothly as possible by using fine sandpaper on the following areas until they’re perfectly smooth though: The guiding tabs of the bolt carrier, the underside of the bolt carrier that’s riding on the hammer, the gas piston (since it can contact the walls of the gas tube), the round groove in the receiver beneath the rear sight block (where the gas piston enters the gas tube). Naturally, keeping the system well oiled is also advisable.
    If you’re using an UltiMak or another type of height-adjustable gas-tube on your AK, you will also have to ensure that the gas tube is sitting at the right height and angle to avoid any friction between the gas piston and the gas tube. It is important that you do this with a magazine inserted, as the magazine pushes the carrier upwards in the forward position, so insert an empty magazine, ensure the bolt carrier is in the forward position and then adjust the screws on your adjustable gas tube until the carrier travels as smoothly as possible. (Some real steel gas tubes will require you to place a spacer below the between the gas tube and the barrel; otherwise you will not be able to tighten them down in the necessary position.)
    Keeping the front assembly from loosening: On all of our team’s GHK AKs, the nut holding the front assembly in place wasn’t completely tightened. Thus, the barrel, gas tube and rear sight block started to wobble after the guns had seen a couple of games. I would therefore recommend to take care of this issue right away, as there is not much to it: Remove the gun’s bolt carrier so you can flip over the gas tube retaining pin (so it’s facing to the top), remove the gas tube by pulling it upwards, flip over the small pin at the front of your lower handguard so you can slide the forend cap forwards, remove the handguard and then use a wrench to tighten the locknut.
  • Learning how to properly insert magazines: This might seem like a joke to most of you, as pretty much everyone into airsoft knows how to rock in an AK type magazine. There is something to watch out for while inserting the GHK AK magazines that catches most new users by surprise though: If the front of the magazine is not properly aligned with the receiver, it is possible to lock in the magazine not using its front and rear latch but rather using the rear latch and the feeding lips. When this happens, the magazine will usually sit in the gun at an angle preventing the use of the magazine release to eject it. To get the magazine out of the gun, take a rubber mallet or whatever comparable object you have available and whack the rear of the magazine to rock it back out. Be aware that this can potentially ruin your magazine’s feeding lips. If that’s the case, you can check “Taking care of misfeeds #1” to read up on how to replace them.

While that should get you ready to go out and play, there are still some things that can (and probably will) go wrong down the road if you’re using your GHK AK as a skirmish gun. Here are some of the most common issues you might run into after a while of using the gun:
  • Nozzle breakages: The nozzle is riding in the bolt carrier on two tiny tabs. Whenever the nozzle encounters any resistance (like a BB sitting in the magazine too tightly or a jam), these tabs take the full force of the bolt carrier and will sooner or later break. Even though misfeeds are very rare in our teams AKs, all of us had several nozzles lose one of their tabs already. GHK slightly modified the nozzle this year, reinforcing the areas where the tabs are mounted to the nozzle body, but I can say out of experience that they still break. While Samoon advises to just cut off the second tab and keep using the nozzle in that case, this can cause severe jams and I would totally advise against that - it simply doesn’t work.
    Since the only metal nozzle currently available is ProWin’s high-flow model, many of us are stuck with using plastic nozzles, so naturally, there’s a fix for the problem - one that requires a bit of dremeling, mind you. Craft a tiny metal angle piece, dremel a groove into the nozzle the size of the angle piece, use some epoxy to glue the angle piece to the nozzle, drill small hole into the angle piece and additionally fix it to the nozzle using a tiny screw and then use your dremel to grind down the screwhead and the angle piece until the nozzle smoothly slides into the bolt carrier. Of course, your metal tab should not be longer or shorter than the original; otherwise the nozzle might not be centered in the carrier. While this sounds like a bit of work, I can attest that it does provide a long term solution for the nozzle breakages if done properly, as I have not had any of my metal nozzle tabs break so far. Gasguns.info user poper399 posted links to pictures of a modded nozzle in this thread.
  • Disconnector breakages: After you’ve fired a couple thousand rounds through your AK (particularly on full auto), there is considerable chance that your gun’s disconnector will break. It’s no big deal if this happens during a game, as the sear always breaks in a way that will allow the gun to continue functioning on semi auto. However, I recommend replacing the sear with Hephaestus’ steel disconnector. To install it, locate the pin holding the trigger, hammer catch and disconnector, remove the C-clip holding it in place, take note of the positions of all parts and springs, slide out the pin, replace the disconnector and slide the pin back in before installing the C-clip again. You can use a thin screwdriver (or similar) to push out the pin so that the parts other than the disconnector are held in place by the screwdriver while the pin is removed from the receiver.
  • Dust cover lock and trigger breakages: During the first two years in production (correct me if I’m wrong), the GHK AKs came with pot metal triggers and dust cover locks, the latter of which were particularly prone to breakages when the gun was fired with the dust cover removed. For those owning one of these earlier models, Samoon offers the steel parts that are now standard on GHK AKs individually. The installation of the dust cover lock is fairly straightforward: Drive out the pin holding the spring guide in the dust cover lock, exchange the latter for the steel replacement, reattach the spring guide and drive the pin back in. Alternatively, you could just get the Hephaestus simulated recoil spring assembly, which is a complete set that replaces the entire spring assembly. For the installation of the steel trigger, refer to the chapter “Disconnector breakages”.
  • Keeping the gas piston in place: In the original bolt carrier assembly, the gas piston is mounted to the bolt carrier via a threaded plastic cylinder. Plenty of people have reported that this part broke apart after continued use of their GHK AK. While we have not had that happen on our guns, I’ve gone ahead and installed Hephaestus’ aluminium replacement (which they call a “Recoil Kit Aluminium Adapter).
    No matter which adapter you use - plastic or aluminium - the gas piston tends to come loose after a while even if you screw it on tightly, so I also recommend putting some thread lock on the adapter. Make sure to use the kind that still allows you to unscrew the piston by force though; otherwise you’re eliminating the possibility of switching to another gas piston without also replacing the bolt carrier (or vice versa).
  • Bolt carrier breakages: When the nozzle is sitting in the forward position, it is held in the bolt carrier by a couple of tabs that allow gas to exit the bolt carrier while preventing the rear of the nozzle to sag and cause a jam. These tabs can break (possibly due to the stress of the nozzle slamming against them when the bolt carrier returns to battery) and once the bottom four tabs are gone, the carrier needs to be modded to remain usable. Gasguns.fino user Echo2 has posted a guide on how to fix a broken carrier by removing the tabs and using a modified second nozzle stopper to limit the nozzle’s movement and thus keeping it from falling out of the carrier.

Of course, there are also some optional modifications that people have come up with to enhance their gun’s performance or suit it to their liking. Here are a few:
  • Keeping the inner barrel in place: You can slide out the inner barrel by removing the loading ramp from your gun and then removing the hop-up unit from the barrel. As you will probably notice, while the inner barrel doesn’t have a lot of room to move around in the outer barrel, there is room for it to wobble about a bit. There is not enough room to get an O-ring or barrel spacer in there, but what you can do is push the barrel into the receiver as far as possible, (evenly) apply some teflon tape to it as far forward as possible and then slide the barrel forward again. While the GHK might never be an accuracy wonder, this should at least get rid of one factor contributing to that.
  • Making refillable CO2 magazines: To eliminate the need to swap out cartridges after every magazine worth of BBs, user Devilhunter came up with the idea to leave an empty cartridge in the CO2 magazine and replace the screw that sits where the fill-valve would be on the green gas magazines with a KJW M9 magazine fill-valve (since these allow for filling liquid CO2). The magazine can then be filled using a bottle of CO2 with an adaptor. Keep in mind that the metal of the cartridge will fatigue with every refill. While there are certainly users running this setup since a while, I have not given it a go and cannot attest to its safety.
    Since you can buy the output valves of the CO2 magazines individually from Samoon, other users have used these in combination with KJW M9 magazine vill-valves to create refillable CO2 magazines. However, there is a report of one user’s modded magazine blowing up because of worn threading (holding the cylinders). While I was under the impression that the storage cylinders on the green gas magazines are identical with the one on the CO2 magazine and think this incident might not be down to the actual strength of the material, I also cannot recommend this solution due to lack of personal experience. 
    A third option is using a refillable CO2 cartridge like the one offered by KHMountain. These have a fill-valve in the rear of the cartridge, which should enable you to refill them threw the hole in the cap holding the cartridge in the magazine.
  • Installing a left side charging handle: Like most AK models, the stock GHK AKs have to be charged on the right hand side, requiring the shooter to reach over or under the gun to cock the hammer. If you would like to speed things up a bit, you can do that by either getting one of the currently available left side charging kits - see “Hephaestus Charging System Type A” or “...Type B” - or by crafting one yourself.
    The GHK AKs bolt carrier has a threaded hole on its left side that is housing the pin holding the nozzle stopper. What you can do is getting a longer pin with the same threading on it and simply connecting a charging handle to that pin. This will require you to cut away a portion of the dust cover to allow the charging handle to cycle.
    Make sure the bolt is able to go to battery after this information; you might have to remove a tiny bit of material on the left side of your receiver.
    Since charging the gun using a modded charging handle like this will put stress on the threading in the bolt carrier, you might want to consider a steel bolt carrier to go along with this upgrade.

Over the last couple of years, quite a couple of parts for the GHK AK series have popped up on the market. Let’s take a look at what’s on offer and get down to part-specific information. Some of these are just product descriptions, while others come with product related notes:
  • Bolt & recoil spring assembly
    • Bolt buffer - This is the chunk of plastic in the rear of your AK that absorbs most of the recoil and keeps the bolt carrier from coming out. It will move about in the gun a bit, which has led some user to apply some reusable adhesive to it to keep in place. However, there is no necessity in terms of functionality to do this modification. While it is possible that the buffer will show signs of wear from being rocked around by the recoil, this part should generally not break and last you a long time.
      • Daytona Gun Aluminium Bolt Buffer - As part of their steel internals kit for the GHK AK, Daytona Gun offers an aluminium replacement for the bolt buffer. This unit comes with a small removable rubber piece mounted to the front of it, slightly decreasing travel and recoil while increasing the rate of fire. The rubber piece can be taken out to avoid this effect without issue. As the Daytona Gun part has the same length as the original bolt buffer, it too can slightly move about when firing.
    • Bolt carrier - The bolt carrier on the GHK AK is made out of pot metal, and while it does usually hold up for many thousands of rounds, it can indeed break. Refer to the chapter “Bolt carrier breakages” for further information.
      • Creation Steel Bolt Carrier - This is an as of now out-of-production steel replacement for the original bolt carrier. Users have reported that it was quite poorly produced and required modification to work decently, as the gas piston and steel bolt carrier would not line-up properly.
      • Daytona Gun Steel Bolt Carrier - The main piece of Daytona Gun’s steel parts kit for the GHK AK, this is currently the heaviest and the only steel made bolt carrier available for the GHK AK. Keep in mind, however, that in contrast to the original part, this is a three-piece unit consisting of a lower and upper bolt carrier as well as a charging handle. While this means you could theoretically swap out your charging handle for a custom type, in practice you’re going to have to use permanent thread lock to keep the handle from coming loose. The screws between the upper and lower bolt carrier seem less of a cause for worries in that regard, but of course the simple fact of the unit consisting of multiple parts will be a downside to fans of realism.
        Since the carrier is made out of steel, this unit is particularly useful for left side charging handle modifcations using the nozzle stopper pin threads. Check the chapter “Installing a left side charging handle” for more information.
        With around 430g (with no nozzle inserted), the complete Daytona Gun bolt carrier group (with the included gas piston and nozzle stopper) is around 80g heaver than the GHK bolt carrier with Samoon’s heavy gas piston. This has a severe effect on both recoil and rate of fire, the latter of which will fall considerably below the 600rpm of the real firearm when using this part.
        While the steel bolt carrier’s shape is largely identical to the original one, some marginal differences could potentially require you to do a bit of sanding and fine tuning to get it to cycle smoothly. (This was the case on one of our guns while it wasn’t on another.) While the gas piston sits in the carrier at a very slight downwards angle in the original group, it will sit perfectly straight on DaytonaGun’s carrier. Hence, if you’re running an UltiMak or another adjustable gas tube, small height and angle adjustments could be necessary.
    • Dust cover lock - Up until 2012, the dust cover lock - the part holding the dust cover and recoil spring guide in place - was constructed out of pot metal on GHK’s AKs. Hence, it easily broke when the gun was fired without the dust cover on, which puts a lot of stress on the small tabs on the lock that slide into the receiver. Having had the top cover of my AK blown into my face once when I still had the GHK pot metal version of this part, I'd strongly advise upgrading this part if your gun is still outfitted with a pot metal dust cover lock.
      • Daytona Gun Dust Cover Lock - Daytona Gun’s steel replacement of the dust cover lock is the chunkiest of all available versions of this part. While it does not look exactly like a real steel dust cover lock, it does have a couple of advantages: It has a firmer seat in the receiver than all the other available options, making it easier to lock the dust cover in place without accidentally pushing the lock into the receiver. Additionally, it features a much easier to remove pin holding the spring guide in place, meaning that recoil springs and spring guides can be exchanged without a hammer at hand.
      • Hephaestus Dust Cover Lock - See “Hephaestus Recoil Spring & Spring Guide” for more information.
      • Samoon Dust Cover Lock (This is part of the Samoon Fire Control Parts Set - The 2012 (and newer) GHK AK versions are already outfitted with this part by default.
    • Gas piston - While the gas piston has no functionality on the GHK AK other than making sure your bolt carrier is aligned properly when cycling in your gun (as there is no gas pressure coming down the gas tube to push it back into the receiver), it serves as a means to adjust the strength of the recoil and the rate of fire on your gun. The default gas piston is made out of a very light metal, enabling the gun to fire at a much higher rate of fire than its real counterpart and making for rather weak recoil. Several replacements are available on the market.
      • Daytona Gun Gas Piston - This is a heavier replacement for the gas piston and will thus considerably increase the recoil of the gun. It does not come with a stronger recoil spring. Information on the exact weight of the piston would be appreciated.
      • Hephaestus Gas Piston - This is a heavier replacement for the gas piston and will thus considerably increase the recoil of the gun. It does not come with a stronger recoil spring. It is also available in a shorter length to fit AKSU type guns. Information on the exact weight of the piston would be appreciated.
      • Ra-Tech Recoil Power Kit - This is a heavier replacement for the gas piston and will thus considerably increase the recoil of the gun. Apparently, like the Samoon version it comes with a stronger recoil spring. Information on the exact weight of the piston would be appreciated.
      • Samoon Gas Piston & Recoil Spring - The Samoon gas piston comes with a stronger recoil spring and I'd say it makes for the strongest kick among the currently available gas piston sets. Like the Hephaestus version, it is also available in a shorter length to fit AKSU type guns. Information on the exact weight of the piston would be appreciated.
    • Nozzle - The nozzle (or bolt) is housed in the bolt carrier and takes care of propelling the BB and distributing gas backwards to send the bolt carrier to the rear, cocking the hammer. The AKs nozzle does not have a return spring, so don’t be confused by the nozzle remaining in a forward position when the gun cycles.
      To keep the nozzle operating properly, make sure that the two O-rings in its rear are coated with silicon oil and ensure that the nozzle can travel smoothly within the bolt carrier. The forward movement of the nozzle is limited by the nozzle stopper, a small plastic or metal piece held in the bolt carrier via a pin on the side. Make sure this pin is not overly tightened, as this can put sidewards pressure on your nozzle, hindering its movement.
      GHKs nozzle design is one of the weak links in this GBBR system and all currently available plastic variants of it are prone to breakages. Consult the capter “Nozzle breakages” for more information on how to fix a broken nozzle.
      • Action Aluminum Cylinder Bulb - While this looks to me like a replacement for the valve in the nozzle, this wouldn’t make any sense as the original nozzles cannot be opened up. Any more info on this product would be appreciated.
      • FG Airsoft Adjustable Nozzle - This is the only adjustable Nozzle for the GHK AK series as of now. It's being manufactured out of standard nozzles by a small bunch of people in France. Basically, it's a standard nozzle with a small screw pushing in from the side, thereby blocking the path for the gas that's directed forward towards the chamber. While this means that gas flow is a bit off-center, I haven't found this to influence BB trajectory in several years of usage.
      • GHK 1J Nozzle - This nozzle will limit the muzzle velocity to 1J with Green Gas only; CO2 will still yield higher FPS.
      • GHK/Samoon High-Flow Nozzle - Information how this compares to ProWin’s high-flow nozzle would be appreciated.
      • ProWin CNC-Machined Aluminum High-Flow Nozzle - The ProWin nozzle is currently the only metal nozzle available for the GHK AK series and - since it uses a high flow valve - it yields a muzzle velocity gain of around 10% in my experience.
        This nozzle is a bit longer than the original ones and can potentially keep the bolt carrier from moving all the way forward. This can be remedied by simply dremeling or sanding off a bit of the rear of the nozzle.
      • Samoon Blowback Nozzle - This is basically a nozzle specifically designed to maintain full blowback power even without any BBs in the chamber, so it's ideal for fooling around with the gun indoors or movie prop use.
    • Nozzle stopper and pin - See “Nozzle” for more information on this part.
      • Daytona Gun Nozzle Stopper - Daytona Gun offers a metal replacement for the nozzle stopper. It does not feature a sloped ramp like the original, and I’ve found the nozzle cycling to be smoother with the original part. Since there is little stress exhibited on this part, nothing I can think of speaks against using the original GHK plastic part. Daytona Gun’s nozzle stopper does come with a higher quality steel pin holding it in place, however. The steel pin is compatible with the original GHK nozzle stopper.
    • Recoil spring & spring guide
      • Hephaestus Recoil Kit Aluminium Adapter - This replaces the small threaded cylinder connecting the bolt carrier and the gas piston. It is advisable to place a tiny amount of thread lock on the threads before assembly to assure that the bolt carrier and the gas piston will not fall apart during firing.
      • Hephaestus Recoil Spring & Spring Guide - In contrast to the other recoil springs on the market for the GHK AK series, the Hephaestus version seems to come with a replacement for the spring guide as well. The interesting part about this is that this replacement is a two-piece guide like on the real AK, so this might also be a product for the realism fans among you. However, the spring on this set is weaker than the Samoon enhanced recoil spring and because of the longer spring guide, you do need to pay attention when installing the part to make sure that the spring guide is properly seated in the bolt carrier. If that’s not the case, the bolt carrier will not be able to recoil all the way to the buffer, putting the stress of the recoil on the spring guide and dust cover lock, which can lead to the dust cover lock breaking.
  • Trigger & hammer assembly
    • Auto lever - Sitting on the right side between the hammer and the magazine, this part keeps the hammer from dropping when the bolt carrier is not in the most forward position, ensuring that gas is only released to the nozzle once it has returned to battery. While it will generally never break, you can replace it by removing the C-clip that sits on the right side of the empty magazine lever on the pin that’s holding it, remembering the position of all the parts and springs and then pulling out the pin. Keep in mind that while the auto lever should be pushed to the rear by the spring resting on it, the empty magazine lever should be pushed forwards by its corresponding spring.
      • Daytona Gun Steel Auto Lever - This is a steel replacement of the otherwise identical original part. Refer to “Auto lever” for instruction on how to remove the old auto lever in order to replace it.
    • Disconnector - This sear interacts with the selector lever and the trigger to determine the fire mode of your gun. When the selector is set to auto, it keeps the disconnector from catching the hammer in between shots, thus making your gun fire as long as you hold the trigger or the magazine runs dry. Set the selector to safe, and trigger movement is prevented altogether. 
      The disconnector is one of the pot metal internals that tend to break on the GHK AK after a couple thousand rounds have been fired. There are several replacements available. You can read the chapter “Disconnector breakages” on how to install them.
      • Action Steel Semi-Auto Disconnector - This is a steel replacement for the disconnector. In contrast to Hephaestus’ Steel Disconnector, this version will remove your gun’s capability to fire in full auto, which might be important for those of you living in countries where only semi auto airsoft guns are allowed. Check the chapter “Disconnector breakages” for installation guidelines.
      • Azimuth Steel Semi-Auto Disconnector - This is a steel replacement for the disconnector. In contrast to Hephaestus’ Steel Disconnector, this version will remove your gun’s capability to fire in full auto, which might be important for those of you living in countries where only semi auto airsoft guns are allowed. Check the chapter “Disconnector breakages” for installation guidelines.
      • Daytona Gun Steel Disconnector - This steel replacement comes with a grub screw inserted at the bottom. While this might be a downside to realism fans, it allows the user to finetune the disconnector travel, which is useful when using selectors with different specs than the original. Check the chapter “Disconnector breakages” for installation guidelines.
      • Hephaestus Steel Disconnector - This is a steel replacement for the disconnector. Check the chapter “Disconnector breakages” for installation guidelines.
      • Team GBB Disconnector - This is a CNC-machined aluminium replacement for the disconnector. Check the chapter “Disconnector breakages” for installation guidelines.
    • Empty magazine lever - Located infront of the hammer on the left side, this part is being pushed backwards by the lever on the magazine connected to the BB follower once all BBs in the magazine have been fired, thus locking the hammer in the cocked position and keeping your gun from firing when there is no ammunition in your magazine. It generally never breaks, but can be removed. See the chapter “Auto lever” for more information.
      • Daytona Gun Steel Empty Magazine Lever - This steel replacement differs slightly from the original design and might need a bit of a break in period in order to operate smoothly. See the chapter “Auto lever” for more information.
    • Firing pin (Valve knocker) - The firing pin is pushed forwards every time the hammer drops and thus opens the gas output valve of the magazine. A small small spring connects the firing pin to the trigger assembly and returns it to its default position after firing. 
      Like the rest of the trigger assembly, it is made from pot metal. While I have not personally experienced or heard of the firing pin break, there are several replacements available.
      • Daytona Gun Steel Firing Pin - This is a steel firing pin that is largely identical to Hephaestus’ and the original version.
      • Hephaestus Steel Firing Pin - This is a steel firing pin which is identical to the original part in terms of its design.
      • ProWin Steel Firing Pin - The ProWin firing pin replacement is designed specifically to work best with the ProWin magazines and requires modification of other parts to function properly. Check ProWin’s YouTube channel for further instructions.
        As the ProWin magazines for the GHK AK are rather badly made and in my opinion inferior to the other options available, there is no reason to get this firing pin over the Hephaestus one in my opinion.
    • Hammer - The force of the hammer dropping pushes the firing pin to the front and thus opens the gas valve in the magazine. 
      In contrast to the real hammer, the GHK version only uses one spring, although a second modified (inverted) spring can be used on the left side of the hammer to increase the performance of your gun. The additional force the second spring exempts on the bolt carrier by pushing the hammer upwards in a cocked state is negligible in terms of the smoothness of the action, while in my experience the muzzle velocity increased by a small amount. 
      To test whether your hammer and firing pin work smoothly, insert an empty magazine into your gun, remove the bolt carrier and drop the hammer (by holding manually pressing the pin that prevents the hammer to drop when the magazine is empty to the front). Now, move the hammer backwards until it almost touches the catch on the trigger assembly and let it go again. Remember that the resistance the pin encounters is considerably higher when the magazine is filled, so if the hammer doesn’t drop smoothly and fails to properly open the valve during this test, you might want to sand the surface where the pin rides on the hammer or install a second or stronger hammer spring.
      The original pot metal hammer can take take a beating, but over the years will start to be quite worn out. To install a new hammer, simply remove the C-clip from the pin holding it - which is located on the inner left side of the receiver, remember the position of all the springs and parts and pull out the pin. When you’re putting your hammer assembly back together, make sure that the firing pin is attached to the small return spring and properly seated in the notch at the bottom of the hammer.
      • Daytona Gun Steel Hammer - This is a much more hefty steel replacement for the original hammer. Getting it to work can prove to be a bit tricky though, as at least on our guns, the resistance between the hammer and the firing pin was too high for the hammer to properly push the firing pin forwards. This might or might not have to do with the hammer missing the sloped underside found on the original hammer. Either way, sanding all the contact patches until they hammer drops smoothly can alleviate the problem. See “Hammer” for installation information.
    • Hammer catch - When firing the gun on semi auto, this part sitting inside the trigger will catch the hammer after you depress the trigger and the disconnector lets go of it. Even though it is made form pot metal, I have never heard of this part breaking and you will probably never have to replace it. If you do want to install a new hammer catch, refer to “Disconnector breakages” for a guideline.
      • Daytona Gun Steel Hammer Catch - This is an otherwise identical steel replacement for the hammer catch. Refer to “Disconnector breakages” for a an installation guideline.
    • Trigger - While the trigger itself probably won’t require explanation, it is worth being mentioned that up until 2012, the GHK AKs came with pot metal triggers. If you’re looking to replace one, you can pick up one of the following units and consult the chapter “Disconnector breakage” for installation tips if needed.
      • Daytona Gun Steel Trigger - Daytona Gun’s steel trigger is a two-piece design and differs from the original as well as the real steel part in that regard as well as by being quite a bit chunkier. Currently, I see no reason to use a two-piece trigger when the Samoon steel trigger is available, so I’d go with the Samoon version instead. Check the chapter “Disconnector breakages” for installation guidelines.
      • Samoon Steel Trigger (This is part of the Samoon Fire Control Parts Set.) - This trigger comes as standard on all 2012 (and newer) GHK AK models. Check the chapter “Disconnector breakages” for installation guidelines.
  • Fire selector - Unlike its real counterpart, the selector lever on the GHK AK is actually screwed to the selector, which is hard to notice since the screw looks more like a rivet and does not have a notch to insert a screwdriver. You can, however, unscrew it using pliers or a ratchet, in order to exchange one of the parts.
    In order to remove the selector, take off the aforementioned screw and lever, remove the C-clip on the right side of the selector (inside the receiver), turn the selector to the nine o’clock position (this might require you to press the trigger to get the disconnector out of the way) and then slide it out to the right side of the receiver. Take care to properly place the lever on the selector when reassembling the parts, as the selector actually has a small bump in the shape of the hole in the lever to ensure that both parts stay properly aligned.
    • Selector - The original pot metal selector should never fail you, but if you do need to remove from your gun, see the above chapter “Fire selector” for advice if needed.
      • Daytona Gun Steel Selector - This steel replacement differs a bit from the original (as it is much chunkier) and Daytona Gun have confirmed that their might be a bit of a tolerance issue when trying to install it. It will generally be a bit harder to click insert and click into place and removing it will usually take considerably more force. 
        Its main problem, however, is that it does not have a notch for a C-clip, allowing the selector to stick out of the receiver a bit further than the original and thus making for less resistance in the movement of the lever. While this could vary depending on the exact shape of your receiver, I found the feedback when switching the lever lacking. Check “Fire selector” for installation advice.
    • Selector lever - While your fire selector will typically never break, there are a couple of “tactical” replacements available on the market.
      • Dynamic Star Mark IV Enhanced Safety - This is a tactical fire selector with a notch to lock the bolt in a backwards position and with a tab to enable the user to move the selector with the right index finger. However, since the bolt of the GHK AK series cannot actually travel all the way back, the notch on this fire selector is actually useless; it cannot engage the bolt. 
        Check “Fire selector” for installation advice.
      • Hephaestus Tactical Selector - Like the Dynamic Star Enhanced Safety, this is a modified selector lever with a tab allowing for right hand operation (provided you're strong enough to move the selector with just your finger). Contrary to the Dynamic Star product, this version does not possess a notch to lock the bolt in the rearward position. However, since this notch is not usable on the GHK AK series anyway, as the bolt cannot travel back far enough, this is actually a benefit, as the notch would just serve as another opening for dirt to get into the gun.
        Check “Fire selector” for installation advice.
      • Hephaestus Left Side Selector - This is technically not an available part, but a modification that Hephaestus will do to a limited quantity of guns in their shop. Follow the link for more info.
  • Hop-Up & barrel
    • Hop-up chamber - The stock GHK AK utilizes a plastic hop-up chamber with a wheel type adjuster pushing down on a small cylindrical rubber piece. It is held straight on the barrel via the usual plastic clip and serves as the only mounting point for the inner barrel. (See “Keeping the inner barrel in place” for more information on this aspect.)
      The design of the hop-up chamber can lead to misfeeds in rare cases, as the BBs running up the loading ramp into the chamber will typically crash into the bottom of the chamber and can potentially be thrown off course that way. If you’re looking on how to alleviate this problem, consult “Taking care of misfeeds #2” above.
      Since misfeeds can lead to BBs being jammed between the nozzle and the hop-up chamber, the plastic hop-up chamber is prone to breakage. To replace it, undo both screws holding the loading ramp in place, remove the ramp and push the inner barrel into the receiver (for example using a cleaning rod), enabling you to remove the hop-up unit and rubber form the barrel. Take care not to lose the small cylindrical rubber piece resting in the rectangular cut-out at the top of the unit.
      • A Plus Hop-Up System - Available in three lengths, this is a set replacing the inner barrel, hop-up unit and hop-up rubber. While the GHK AK normally utilizes AEG type inner barrels, A Plus went for a 6.03mm stainless steel barrel with a GBB type cutout. Installation can be a bit finicky, as the hop-up unit is held on the barrel using two grub screws that have to be tightened completely evenly for the hop-up unit to be centered on the barrel. Additionally, the unit can rotate on the barrel, so the screws have to be tightened when the hop-up unit is perfectly seated as otherwise the hop- effect will be applied at a slightly incorrect angle. Results with this set seem to vary quite a bit and range from horrendous muzzle velocity losses to nice range gains. If you’re experiencing fps losses using the A Plus Hop-Up System, make sure that the hop-up unit has no room to move back and forth. 
      • FG Airsoft Metal Hop-Up Unit  - This is a steel hop-up unit with a rectangular cut-out. As of now, I have no information on its fit and quality. See “Hop-up chamber” for installation instructions.
      • ProWin Metal Hop-Up Unit - ProWin's metal version of the hop-up unit is made of aluminium. I tried it on one of our guns and actually had to screw out the barrel by one turn to be able to squeeze it in there. If you are forced to do the same, make sure to check if the nozzle still seals correctly with the packing on the magazine by applying some removable color to the gas inlet on the bottom of the nozzle and then inserting a magazine while the bolt carrier is in the forward position. Remove the magazine and check the color imprint on the magazine packing to see whether the nozzle’s gas inlet fully covers the hole in the packing.
      • Team GBB Metal Hop-Up Unit - This is a steel replacement of the hop-up chamber. While it is a better fit than the ProWin unit, the Team GBB unit has just a small hole instead of a rectangular window for the small rubber piece applying pressure to the hop-up rubber. Thus, pressure on the hop-up unit will be limited to a smaller area than with the ProWin and stock units. See “Hop-up chamber” for installation instructions.
    • Hop-up rubber - Since the GHK AK utilizes AEG type inner barrels (unless you’re using the A Plus set), a vast selection of hop-up rubbers is available for this gun. Here are some popular choices (which you can install using the guidelines provided in “Hop-up chamber”.
      • KM RH55/65/75 - This rubber is favoured by some GHK AK users due to the shorter lips it has, making this an good rubber for modified hop-up chambers with a groove at the bottom. It features a notched contact patch.
      • Maple Leaf Monster (Diamond) - With its very large notched contact patch, this hop-up rubber is currently quite popular with the AEG crowd. It is available in different grades of hardness and many report that it does it’s job equally well in a GBBR.
      • Samoon Marvellous Hop-Up Rubber - As of 2012, this is the stock rubber on GHK AKs. Its short but bulky lips aid in avoiding misfeeds and providing a very tight seal, but the simple smooth BB contact patch makes for mixed results in terms of hop-up efficiency.
    • Inner Barrel - The GHK AK utilizes AEG type inner barrels. As such, you can replace the stock barrel with your favourite brand of precision barrel. If you’re new to GBBRs, do keep in mind that barrel diameter and length will have a fundamental effect on your gun’s muzzle velocity. Going from a standard AKM length barrel to a 6.03mm version of the same length yielded a gain of over 50fps in the case of my own gun, for example.
      To install a new barrel, remove the hop-up components as described in “Hop-up chamber” and then slide out the old barrel to the front of the gun.
    • Loading ramp - This plastic loading ramp acts as a guide for BBs being pushed from the magazine into the chamber by the nozzle.
      It will typically never get damaged, but make sure to remove BB residues from it from time to time if you’ve had misfeeds resulting in crushed BBs.
      Note that if your outer barrel is screwed too far into the receiver, your loading ramp will  be rather hard to screw into the receiver. Check “Outer barrel” for further info on this.
    • Outer barrel - The outer barrel is pretty much the only exterior metal part on the GHK AK that is not manufactured from steel. If you're planning to do push-ups on your AK, maybe consider getting one of the available steel outer barrel upgrades. 
      To install a new outer barrel, you will have to remove the rear sight block, gas block, frontend retainer, front sight and flashhider from your existing barrel. While the flashhider can just be screwed off as usual (Don’t lose the spring and pin holding it in place!) and the frontend retainer just has to be slid off the barrel, the other three parts are held on the barrel by grub screws (at the bottom of the parts) and pins driven in from the side. Remove the grub screws, drive out the pins from the left side, put the parts aside, loosen the nut holding the barrel in place, unscrew the barrel, swap the lock nut over to the new barrel and mount it to the receiver. Mount the lock nut, rear sight block, frontend retainer, gas block, front sight and flashhider in that order, driving in the three pins from the right side. Leave the pin fixing the rear sight block out for the time being so you can still turn the barrel. Make sure to screw the barrel into the receiver far enough to not allow the hop-up unit to move around, but don’t screw it in too much or your hop-up will be under excessive pressure and the bolt carrier will not be able to fully go to battery anymore as it will hit the rear sight block. After driving the pin into the rear sight block from the right side, make sure that the rear sight block does not protrude into the receiver - it should sit flush with the block it rests on. Afterwards, make sure to check if the nozzle still seals correctly with the packing on the magazine by applying some removable color to the gas inlet on the bottom of the nozzle and then inserting a magazine while the bolt carrier is in the forward position. Remove the magazine and check the color imprint on the magazine packing to see whether the nozzle’s gas inlet fully covers the hole in the packing.
      • Azimuth Steel Outer Barrel - The Azimuth Steel Outer Barrel is also available for the GHK AK105. See “Outer barrel” for installation guidelines.
      • GHK/Samoon Steel Outer Barrel - The Samoon version is the most expensive of the three available steel outer barrels. See “Outer barrel” for installation guidelines.
      • GunsModify Steel Outer Barrel - The GunsModify version is the most affordable of the three available steel outer barrels. See “Outer barrel” for installation guidelines.
      • Team GBB Steel Outer Barrel - As far as I know, Team GBB are currently the only ones offering a steel replacement for the shorter AKSU barrels. See “Outer barrel” for installation guidelines.


In addition to that, companies like Asura Dynamics, Dynamic Star, Hephaestus, LCT, RA Tech, Samoon, TAF and many more offer external parts like barrels, sling mounts, sights, gas blocks, rail systems and other forends, grips etc. that are compatible with GHK and LCT AKs which I have not listed here simply because that list would be endless.
Keep in mind that you can also use grips, forends, some stocks, gas tubes and many other parts from real AKs as well. 
In the following, I will just go over a couple of exterior parts developed specifically for the GHK AK series. Again, please let me know if you feel that something is missing from this list.
  • Angrygun AR Grip Adapter - While this part obviously allows you to use AR type grips on your AK, I have no information on whether it supports AEG or real steel grips, although I’d assume the latter.
  • Dynamic Star V Type Stock Pipe - This is a stock tube that allows the use of an AR-style retractable stock on the GHK AKs with a solid stock receiver. It’s made out of aluminium and features a steel ambidextrous QD sling mount.
  • Hephaestus Charging System Type A - The original Ratchet Charging System is a gas tube with an opening on the left side designed by Dublin AK Systems. This allows for left-side charging in the same manner as you'd charge an H&K MP5 or G3 type weapon. Like on the MP5 and G3, the bolt can also be locked in a backwards position. The charging handle sits inside the gas tube infront of the gas piston and thus remains stationary while firing to avoid injury. The Type A charging system is made from steel.
    Keep in mind that the small diameter of the cylinder sitting inside the gas tube will not allow you to run a Samoon or Daytona Gun gas piston. I’m not sure on whether the product is compatible with Hephaestus and RA Tech gas pistons; information on this would be appreciated.
  • Hephaestus Charging System Type B - The second generation of the Ratchet Charging System combines an UltiMak style railed gas-tube with a charging handle sitting inside the gas tube, allowing left side charging handle. The charging handle sits inside the gas tube infront of the gas piston and thus remains stationary while firing to avoid injury. Due to the space used for the charging handle, the rail on this system sits higher than on an UltiMak, meaning you probably won't be able to co-sight with it. The Type B charging system is made from aluminium.
    Keep in mind that the small diameter of the cylinder sitting inside the gas tube will not allow you to run a Samoon or Daytona Gun gas piston. I’m not sure on whether the product is compatible with Hephaestus and RA Tech gas pistons; information on this would be appreciated.
  • Hephaestus Charging System with Modular Rail Forend - This is a version of Hephaestus Type B charging system for the shorter AKSU/AKMSU type guns that comes with a rail forend replacing the lower handguard. The charging system functions identically as the regular Type B unit.
  • Hephaestus Folding Stock Adaptor with 6-position Extension - This is a 6-position stock tube that allows the use of an AR-style retractable stock on the AK105, AK74M and AKS74U. It’s made out of aluminium and features a steel ambidextrous QD sling mount.
  • Hephaestus Stock Adaptor with 6-position Extension - This is a 6-position stock tube that allows the use of an AR-style retractable stock on the GHK AIMS and AKM. It’s made out of aluminium and features a steel ambidextrous QD sling mount.
  • Hephaestus Tactical Magazine Catch - This magazine catch replacement can be operated with the trigger finger, but the tradeoff is that removing the magazine using your thumb will be slightly more akward.
  • Hephaestus Top Rail - Replacing your adjustable rear sight with a fixed one, this unit provides some rail space on top of your AK’s dust cover. It can be fastened with a grub screw in the rear to avoid wobble and can also tilt upwards to allow for dust cover removal. This is noteworthy as many similar products have the rail bolted directly to the cover, which is usually not a wobble-free solution even when the dust cover is mounted to the rear sight. However, the tradeoff is that using this top rail you eliminate the possibility to open up your AK without the use of tools. 
  • Samoon Butt Stock Adaptor - This part will allow you to mount a stock tube for a retractable stock to your GHK AK105, AKS74U or AK74MN.
  • TAF Stock Adapter & Stock - TAF currently offers an adaptor for the AKM and AIMS rifles in combination with a range of different solid stocks: Plum Stock, Wood Stock, AIM Md. 63 Stock and RPK Wood Stock


A variety of different magazines is available for the GHK AKM. The Pro-Win magazines aside, all of them can be used with every type of AK, meaning that an AKM can be used with 5.45x39mm type magazines and an AK74 can be used with 7.62x39mm type magazines. Here is a quick overview of what’s on offer:
  • Magazines (More info coming soon)
    • GHK Green Gas Magazine (More info coming soon)
    • GHK CO2 Magazine (More info coming soon)
    • Hephaestus Custom Green Gas Magazine (More info coming soon)
    • Hephaestus Custom US Palm Green Gas Magazine (More info coming soon)
    • Pro-Win Green Gas Magazine (More info coming soon)
  • Output valves (More info coming soon)
    • Action High-Flow Valve - This is a high-flow valve for the green gas magazines. There is also a CO2 version of this product, as far as I'm aware.
  • Like 12
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"Samoon Butt Stock Adaptor - This part will allow you to mount a stock tube for a retractable stock to your GHK AK105, AKS74U or AK74MN."


Welp I just finally made my CAA one not wobble. :P This was added to the site recently right?

Also the LCT AK upper rail system can be installed on the GHK you just have to file the bottom of the hole a bit where the dust cover lock goes in. It's wobble free.

Edited by Zereck
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Thanks for the feedback, everyone!

I've been trying to update the guide with some more stuff (like typical setups, muzzle velocity measurements etc.) and the info you provided, but it won't let me edit the post anymore. I've tried to reach out to the mods to see if that can be changed, but so far I wasn't able to get ahold of anyone.



Actually, I found switching from gas to co2 mags using this nozzle did not change the FPS at all.



Interesting. When I tested that, I had already installed my tightbore barrel, so the muzzle velocity of my gun was higher than that of a stock setup anyway, but I still recall a clear difference in fps between green gas and CO2 even with the 1J nozzle. I will test this out again and update the guide once I can.

Edited by Hetzer
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  • 1 month later...

Hetzer I've tested it with both nozzles and there is no difference.


Fish you'd be best off buying one from samoon. It's a PITA to try and load without it.

I know! I wasn't able to use that mag while playing. I bought some used mags and they were really worn it. It was a breeze to load them in from the top



Sent from my iPhone using Tapatalk

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  • 6 years later...

Thanks Hetzer for this great GHK AK's tutorial.

Very useful for us.

Is there anyone that has a YT video/link  with a trigger + hammer group dissasembly and re-assembly on the GHK AK plateform ?



Edited by Raydee
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