VFC HK416 CAG AEG Shop Custom Disassembly

Last time, we examined the appearance and shooting performance of a shop-customized VFC HK416 CAG AEG.

This time, we'll take it apart and see what's inside.

Let's start disassembling it right away.

Disassembly of the exterior

We will now disassemble the upper receiver. The disassembly method is the same as for the standard M4 series.

Remove the pin indicated in the photo. The pin is designed to stay in place, so do not try to remove it completely.

Once the pin is removed, don't forget to close the ejection cover. I often forget to close it and panic when the upper receiver won't come off.

Incidentally, airsoft guns use a lot of pins, so I recommend having a slightly sturdier one on hand for maintenance and disassembly.

Next, close the spent cartridge cover.

Then, you can disassemble it by sliding the upper receiver forward.

If you look at the removed upper receiver, you'll see a hop-up chamber, so let's remove that as well.

Let's take a look at the remaining lower receiver. The nozzle has been replaced with FireFry's Dendenmushi nozzle.

Next, we'll disassemble the stock pipe.

If you remove the stock, you will see a Phillips head screw at the back of the pipe.

Removing this screw is tricky and requires a long Phillips head screwdriver.

Vessel extra-long screwdriver +2 x 300

This makes disassembly easy, so it's useful when disassembling M4-style stock pipes.

Next, we'll disassemble the grip.

The grip is secured with a hex bolt, so we'll remove that first.

The large slotted screw in the middle is for adjusting the motor's position, so you don't need to touch it.

This is a grip with the lid open.

The wiring and motor are connected with faston terminals, so disconnect them.

Remove the two Phillips head screws visible deep inside the grip, and the grip will come off.

Let's take a look at the motor that was removed.

The VFC MK18 mod1 I previously reviewed came with a plain black motor, but this product comes with a plain silver motor.

Upon investigation, it appears that the gearbox components have been updated; the black motor is the old version, while the current one is silver.

Regarding the gearbox version, the MK18 mod1 I previously introduced is the first generation to eliminate spring shims and adopt QD (Quick Discharge) technology. You can distinguish it in its finished state by the fact that the cylinder is black, so the color visible through the hole in the ejection cover when you pull the charging handle is black. Incidentally, this type does not have a FET (Field-Effect Transistor).

For reference, VFC MK18 mod1 AEG

The newer gearbox is the second generation, featuring the elimination of spring shims, the adoption of QD (Quick Discharge) technology, and standard FET (Field-Ejector). You can distinguish it from the other version in its finished state by the fact that the cylinder is red, so the color visible through the hole in the ejection cover when you pull the charging handle will be red.

Knowing this will allow you to determine the specifications of VFC's gearbox.

Both are pretty good, so personally I don't mind either one (though I don't like the spring shim from before), but if you're going to use it straight out of the box or if you want an FET, you should check it out.

From what I saw at several well-known shops in Akihabara during June, July, and August of 2021, not all of them were from new batches; there was a mix of old and new stock, so I recommend asking a shop employee to confirm (they may have long-term stock items).

If you're using online shopping sites like Yahoo! Auctions, it's a good idea to check with the seller or shop.

Incidentally, in my personal opinion, both are fairly good motors, comparable to the Tokyo Marui EG-1000 (with slightly lower RPM and slightly higher torque).

With either motor, using the stock 18:1 gear ratio and a 1200mAh LiPo battery at 25C 7.4V with a storage voltage of 7.6V, it can fire over 15 rounds per second, which is pretty good.

Next, we will disassemble the lower receiver.

Remove the pins holding the gearbox in place. Their location is indicated in the photo. Be careful, as there is a specific direction in which to remove them.

Next, remove the bolt release lever. This is also only held in place by a pin, so remove it by pulling the pin. However, be careful as it has a specific orientation.

Next, remove the magazine catch.

Unlike Marui products, here you first press the magazine catch button and then rotate the raised magazine stopper counterclockwise to remove it.

Now that all the parts holding the gearbox in place have been removed, put the selector switch into semi-automatic mode and remove the gearbox.

The steps up to this point are almost the same for any STD M4 series rear wiring, regardless of the manufacturer, so please feel free to use this as a reference.

I've gotten used to it, so even someone as clumsy as me can do this in less than 15 minutes.

Disassembling the gearbox

Let's disassemble the gearbox.

First, we'll remove the bolt release lever mechanism.

Remove the clip holding the spring in place using needle-nose pliers.

Next, while holding the spring in place with your finger to prevent it from flying off, remove the screw.

Next, we remove the mainspring using the now-standard QD (Quick Discharge) method.

Next, you can open the gearbox by removing the screws that hold it in place. Don't worry if you forget which screw goes where. I'll show you a way to figure out the correct placement by looking at the screws and screw holes later.

This is the opened gearbox.

After that, you can completely disassemble it by carefully removing the parts.

Check each component

First, let's look at the gearbox itself.

This is my favorite 8mm ball bearing specification.

The grease has been applied thinly and carefully overall, but it feels like there's a little too little. The FCU Leviathan uses a physical switch, so it should be fine to apply a bit more grease.

Next, let's look at the FCU and trigger area.

The leaf spring, a characteristic feature of the Leviathan, is not quite reaching the trigger and is not functioning properly, so it needs adjustment.

We will now remove the circuit board.

This is the upper base.

I haven't bothered to check the components installed, but I can see a trigger switch, a reset switch, and a Bluetooth module.

This is the back side.

The main CPU is located on the back.

This is the lower part of the base.

This has a switch that detects the cutoff peak of the sector gear. I'm not entirely sure, but is the blue wire a power supply line for the FCU?

This is the back side.

This one had a sensor to detect the selector's position.

From a quick glance, it seems like even someone like me could do it by combining popular Raspberry Pi or Arduino with sensors and Bluetooth modules, but considering the development time and cost, it's cheaper to just buy an FCU (Functional Control Unit).

Next time, I'll try making a compatible FCU for LMGs, since there isn't one available (I'm not sure whether to use the LCT PKP or the A&K M249).

The next part to be changed is the trigger. It was a type where the trigger pull distance could be adjusted.

There is a grub screw, and the amount of extension can be changed to alter the pull distance.

Next is the piston.

The piston head is original, but the piston itself is a 14-tooth, all-metal piston made by SLONG.

Finally, the nozzle is shaped like a snail.

I'm curious about the red cylinder, but since I'm using the black cylinder from the previous VFC gearbox in my MK18, I can't make an accurate comparison. However, I feel like the position of the acceleration holes has shifted slightly to the back, resulting in a larger air volume.

This isn't a very accurate comparison, so please use it only as a reference.

Finally, the selector plate was modified to accommodate the FCU Leviathan.

The remaining parts are exactly the same as before, so please refer to the VFC MK18 mod1 AEG disassembly guide I previously posted.

Next, let's check the AOE adjustments.

It's not very good. There were no signs of adjustments being made.

Next, I checked out the feel of the shim adjustment.

The only thing that bothered me was that the sector gear clearance was a little too large, but otherwise it was pretty good. So I think the gear noise is caused by either a mistake with the bevel gear shim or poor quality pinion gear.

This concludes the introduction of each component.

Chamber, packing

Next, let's look at the chamber and packing.

The barrel is probably around 275mm, the original part. Personally, I like VFC inner barrels with an inner diameter of 6.05mm; it feels just right.

The chamber appears to be the original part, and the gasket seems to be a Maple Leaf gasket with a hardness of 60.

The way the protrusions came out was just right.

Summary and future plans

Overall, it was a safe and unremarkable build, and it seemed like they only used the bare minimum of parts necessary for the FCU Leviathan to function properly (reinforced pistons).

The ballistics customization appears to involve using the stock chamber and barrel with a snail-type nozzle and a Maple Leaf-type hop-up bucking.

What bothered me was that the grease was very thin and insufficient overall, and the quality of the grease didn't seem very good, so I'd like to change it.

Looking ahead, since it already has an FCU (Fire Control Unit), I'd like to set the cycle rate to the limit of single-sector operation, adjust it with the FCU, and set a usable range for more playability.

I'd like to reuse as many parts as possible from custom-made components that seem usable.

Next time, we'll be covering customization, so please join us if you're interested.

I think the closest match in terms of specifications to the VFC HK416A5 is the one officially sold in Japan.

It's a gas blowback model, but I think the external parts are probably the same.