Last time, I showed you how to disassemble and customize the bolt, lower receiver, and hammer mechanism unit (Z system).
This time, we'll show you everything from assembling the Z system and lower receiver to completion and testing its shooting performance.
First, we'll assemble the hammer mechanism unit.
*This article aims to provide educational explanations from a mechanical engineering perspective regarding the safe hobby use of airsoft guns.
This does not promote acts of violence, the use of weapons, weapon modification, practical evaluation, or violation of laws and regulations.
Assembly of the Hammer Mech Unit (Z System)
This is the hammer mechanism unit (Z system) that we disassembled last time.
It seems that the trigger, which you might want to customize, can only be replaced by disassembling and reassembling the gun to this extent.
We'll start working from here.
Before assembly, we will polish the unplated sliding parts. First, we will polish the inside of the inner frame.
I'll be using my usual Dremel rotary tool to buff the surface.
Dremel High-Speed Rotary 4000
This is my go-to rotary tool that I always use. Having this expands the possibilities of your DIY projects. There are two popular models, the 3000 and the 4000, but I recommend the 4000 because it comes with a set of tools and has more power.
As a guideline for the amount of abrasive material to use, aim for about 0.01 to 0.02 mm. It's difficult to put into numbers, but intuitively, it's about the amount that will slightly remove the paint.
polished areas
This is how we polish unplated sliding parts.
Now that the preliminary preparations are complete, let's start assembling.
When assembling, apply Bellhammer Gold Grease No. 2 while putting it together.
Bellhammer No. 2 Gold Grease
This is a classic, top-quality grease. No. 2 has the same ingredients as No. 0 but with a higher viscosity. I primarily use it for metal-to-metal connections.
Let's start by looking at the hammer.
Remove the pin and then remove the roller.
This roller greatly affects the operation, so make sure to apply plenty of grease to it before assembly.
This is the assembled roller.
We will now assemble these rollers and hammer springs into the inner box.
After assembly, pay attention to the position where the hammer spring is attached.
Next, assemble the knocker and knocker spring.
Care must be taken not to break the knocker spring during installation.
Next, we'll install the trigger bar.
This is what it looks like from the inside, as shown in the following picture.
Assemble the trigger unit carefully, paying attention to the hole positions (if installing an aftermarket trigger, replace it here).
Next, we'll assemble the semi-automatic sear.
Be careful not to lose the spring.
Next, we'll assemble the fully automatic sear.
Be careful not to lose the spring here either.
Now that the internal structure of the hammer mechanism unit is complete, we can close the inner box.
Remember to attach the ring to the hole in the trigger unit.
Finally, fasten the inner box with three screws.
Next, we'll assemble the bolt stop release lever.
Be careful of the springs here too.
Next, we'll assemble the slit cover.
Finally, assemble the bolt catch B (the highlight of the Z system) and you're done.
I've shown you how to disassemble and customize the trigger unit, but if your budget allows, I think it's also a good idea to install an aftermarket trigger unit. In particular, if you want to change the design of the trigger and find disassembly and reassembly troublesome, you could try replacing it with a trigger box that has your preferred trigger already installed.
G&P CNC Adjustable Trigger Box
It's quite expensive, but I think it's the best aftermarket trigger box available. It seems the trigger pull is adjustable.
GUNS MODIFY Steel CNC Adjustable Tactical Trigger (Straight Type)
It has a straight-type trigger that is adjustable. You should be able to assemble it by referring to the article.
Almost all parts, except for the trigger, are available from third-party manufacturers, so you can choose and assemble them to your liking for a more enjoyable experience.
Lower receiver assembly
Now we'll install the hammer mechanism unit (Z system) that we've assembled so far into the lower receiver.
The hammer mechanism unit is a light press-fit, so assemble it carefully by gently tapping it with a plastic hammer.
It is assembled.
Insert the pin to secure the hammer mechanism unit.
Tighten the screw at the rear end of the hammer mechanism unit.
Next, we'll install the magazine catch.
Close the trigger guard.
Next, we'll attach the grip.
To attach the grip, first install the nuts for securing the grip, then attach the grip and secure it with screws.
This is a good opportunity to change to your preferred grip. I've changed mine to my favorite PTS EPG grip.
PTS EPG Grip for Gas Blowback Guns
I wanted the tan color, but only black was available when I tried to buy it. If you go to Amazon, you can choose between black and tan.
Finally, we'll assemble the selector switch. If you're considering replacing the selector switch, the replacement method is the same as described below.
Push the selector switch halfway into the semi-automatic position.
In this state, if you look into the hole from the other side, you'll see that the plunger (pin) prevents the selector's shaft from going all the way in.
Simply push the plunger (pin) in with a flathead screwdriver while turning on the selector switch, and you're done.
I'm completely right-handed and rarely use switches, so I haven't converted my selector to ambidextrous, but I hope this will be helpful for anyone who is considering replacing theirs.
GUNS MODIFY Steel CNC Ambidextrous Selector
If you're right-handed and considering ambidextrous controls, the cutout-type selector on the right side is recommended. The linked product includes both the standard and cutout selectors.
The lower receiver is now complete (with the stock attached).
- No-brand Magpul CTR stock
I think most M4-style stocks, whether for AEG or gas blowback, will fit.
Besides the customizations I've introduced so far, most parts such as the lower receiver itself, magazine catch, and trigger guard are also available for purchase, so it would be fun to choose and assemble them to your liking.
Complete
Once you assemble the bolt and upper receiver, it's complete.
Please refer to the following article for assembly instructions.
When I actually use it in airsoft games, I attach a short scope, flashlight, PEQ replica, and silencer.
Since it's a gas blowback gun, the silencer is just for show. Also, most fields prohibit the use of PEQs and flashlights, so they'll just be for show.
Ultimately, only the scope is actually functioning, but I use it mainly for aesthetic reasons.
Live-fire performance verification
We will now check the actual firing performance.
The conditions were the same as usual: the magazine was filled to the brim with HFC-134a, the surface temperature was 27.2°C (body temperature), and the ambient temperature was around 28°C.
I'm using VFC's 0.2g bio BBs, and the hop-up is set to what I believe to be the appropriate amount.
This is the initial velocity after firing about 10 shots.
This is the launch cycle.
When the cycle was good, it reached 14.7 rounds per second.
The initial velocity and rate of fire are now roughly the same as a standard electric airsoft gun.
In terms of initial velocity progression, at a temperature of 28°C and using 0.2g BBs, it starts at around 90m/s and gradually decreases to about 85m/s after firing a full 35-round magazine.
Gas blowback guns tend to increase in muzzle velocity as the temperature rises, so I think this is a good compromise.
A review of a chronograph.
Fuel efficiency
Next is fuel efficiency.
This is the weight when the magazine is empty of gas.
Next is the weight when the gas tank is full.
It holds approximately 27g of gas.
Finally, here is the weight of a magazine after firing approximately 35 rounds.
Since 8.5g was consumed and 35 shots were fired,0.24g consumed per shotI think it has relatively good fuel efficiency for a long vehicle.
With a full tank of gas, you can fire approximately three magazines, but this can vary considerably depending on the conditions, so two magazines plus a half is probably a more reliable estimate.
Next is a video of it in operation. The conditions are an ambient temperature of 25°C and about half the gas volume.
Tokyo Marui CQBR Block 1 Gas Blowback Custom Semi/Full Bolt Stop Video
I think it was quite sharp.
Ballistics confirmation
I went airsofting and checked the trajectory of the bullets.
The location is Yanex.
It's like a microwave.
The conditions were such that the temperature was around 30℃.
This is a ballistic trajectory image.
With 0.25g BBs and proper hop-up, the muzzle velocity was 81m/s, which is comparable to a regular electric airsoft gun, resulting in a fairly good trajectory.
With accurate aiming through the scope, you can hit a 30cm diameter frying pan at 40m with a high probability. However, since it's a gas blowback gun, the trajectory isn't as stable as an electric gun, so 100% accuracy is difficult.
The hop-up is set to 0.25g, and the hop-up adjustment is optimal at less than half of the fully open setting, so it seems like it could handle heavier BBs as well.
G&G Bio-Bullets 0.2g
It's inexpensive and accurate, so I use it for a wide range of purposes, from performance testing to airsoft games. It's been my favorite since it first came to Japan (around 2008). It lasts a long time for a biodegradable product.
G&G Bio-Bullets 0.25g
It's 0.25g. I generally use 0.25g BBs when playing airsoft.
Summary
In summary, as expected from Tokyo Marui, the operation and performance are excellent, and in terms of durability, I've been using it for about 3 years without any malfunctions. The exterior is also very clean and sturdy thanks to the Cerakote coating.
My biggest selling point is the low price and availability of the magazines. I've had a lot of trouble with other companies' products, so this is a big help (I use five of them).
The only issue is that the initial velocity is quite low, but this can be adjusted by referring to the article, so it's not a problem.
Furthermore, there are many aftermarket parts available, which is great because you can customize it to your liking (though it can be a bit troublesome). Plus, for those who want a finished Mk18, there's the MK18 mod.1, and for those who want a base for customization, there's also the standard M4A1, which is excellent.
You can also enjoy modifying it to resemble a trendy pistol caliber carbine or URG-I.
In fact, the sheer abundance of aftermarket parts available is so overwhelming that you could practically complete the project using only those.
My article describes how to convert the Tokyo Marui Gas Blowback Machine Gun Series CQBR Block 1 to an Mk18 mod.1, but I believe other styles can be modified using the same method.
I don't think the customization difficulty is high, but it might be troublesome if you don't have the right tools. If you have the tools and parts, the process up to this point should take about 4-5 hours.
I hope this information is helpful.
Tokyo Marui Gas Blowback Machine Gun Series CQBR Block 1
This is the base model introduced in this article. You can use it as is, or I think it would be good as a custom base for a 10.3-inch short model (such as a short URG-I).
Tokyo Marui Gas Blowback Machine Gun Series M4A1 MWS
This is the basic M4 MWS. It's so good that it would be a shame to customize the rails, so I think it's best suited for users who want to use it as is. It would be fun to customize the grip, stock, etc. to your liking.
Tokyo Marui Gas Blowback Machine Gun Series M4A1 Carbine
This model is the cheapest in the series, so if you're planning on customizing it, I think it's the best choice (though it's perfectly enjoyable as is). You can do anything with it, from changing the rails to altering the barrel length to make it similar to an SR25.
Tokyo Marui Gas Blowback Machine Gun Series Mk18 mod.1
This is a perfectly finished model. If it had been announced before I made my purchase, I would have bought this one too.
- Spare magazine for Tokyo Marui M4A1 MWS (compatible with the series)
This is a standard 35-round magazine. I use the one that comes with the gun plus four additional magazines for a total of five. Having five gives you plenty of leeway, so I recommend adding four more, but depending on your budget, you can still enjoy the game with just three additional magazines.
- Tokyo Marui Gas M4A1 Series 20-Round Short Magazine (Compatible with the Series)
With a 35-round magazine, it sometimes touches the ground when prone, so I think it's good for marksmen and snipers who often use the weapon prone.
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