VFC MK18 mod1 High Cycle Custom - Completion

The VFC Mk18 mod.1 AEG was supposed to be finished with the previous customization.

However, as mentioned previously, a problem occurred where magazines other than PTS's PMAG could not be fed in full-auto mode.

This time, I'll explain how to resolve the issue, make some minor specification changes, finalize the recipe, and introduce the features of brushless motors.

First, we will examine the problem and the mechanism by which it occurred, and then consider how to deal with it.

Troubleshooting

First, let's consider the fact that this is happening.

This is the incident that occurred.

Let's consider the cause from here.

Therefore, PMAGs, with their strong springs that feed the rounds, can supply ammunition even with short feeding intervals, whereas magazines with normal capacity cannot.

Possible countermeasures include

From these two options, we decided to change the tappet plate, which is easier to manage the risks associated with and can be modified through processing.

The parts procured this time areHurricane E's polymer-reinforced tappet plate for ver.2 will be important.

The reason I chose this one is that, according to rumors, the tappet blades are long, and the nozzle retraction distance is about 1mm greater than that of typical tappets.

This increases the nozzle's retraction distance, which should also increase the timing for feeding rounds. All the parts used in this model will be listed at the end as part of the recipe.

Next, we'll proceed with the task.

Custom readjustment

I've already covered opening the gearbox in a previous post, so I'll skip that part.

Here are the details for disassembling the gearbox. Once you get the hang of it, you can do it in under 10 minutes.

Open the gearbox and remove the tappet.

I will compare the shape of the removed Ronex tappet with the Hurricane E tappet that I prepared this time (apologies, the new tappet has already been modified).

Let's take a closer look at the key points.

The position of the groove that secures the nozzle tip is slightly different; the Ronex has the groove at the front, while the Hurricane E has the fixing groove about 0.3 mm further back.

This would mean the nozzle is always positioned about 0.3mm backward, which increases the likelihood of air leaks and hop-up issues, so we will adjust the nozzle length later.

Next is the blade (same mechanism as a cam).

As rumored, the Hurricane E has longer blades, so it should provide more sweep distance. Therefore, I'll adjust the nozzle and use this tappet.

Here's a diagram illustrating the tips for cutting the feathers (you should be able to do up to about 35 shots per second). This is based on my personal experience, so please use it only as a reference.

Now that the tappets are complete, I will adjust the nozzles to mitigate any potential risks.

It's easy because it's a RetroArms nozzle with adjustable length. This time, the nozzle fixing value is off by about 0.3mm, so I'll add 0.3mm to the previously set 21.2mm to make a nice round 21.45mm.

The nozzle is now complete. Most standard nozzles do not have adjustable lengths, so it is recommended to either use the original nozzle or, if purchasing an aftermarket nozzle, carefully choose one based on the length of the original nozzle.

Next, because the tappet's retraction distance has increased, the timing of the tappet's return is delayed, which could lead to the nozzle not closing in time and potentially causing an air leak. Therefore, we will take measures to address this.

Furthermore, while the target performance was assumed to be 25-30 rounds/second per cycle, it was found that with a fully charged battery, it can reach 32 rounds/second, so countermeasures are needed.

The corresponding part is the tappet spring. By forcibly shortening this spring and increasing the initial load, the tappet returns faster.

If you stretch it too much, the material will undergo a phenomenon called yielding (plastic deformation) and lose its function as a spring, so shorten it by a moderate amount of about three turns.

The method is simple: bend the spring one coil at a time with needle-nose pliers (like straightening it up). Trying to bend three coils at once requires a lot of force and can stretch the spring too much and break it, so it's recommended to do it one coil at a time.

Cut off any excess parts and assemble.

If you're interested in materials or mechanics of materials, please take a look.

Now that the preparations were complete, I was checking the parts before assembling when I stumbled upon something unbelievable.

This.

There was a scratch on the inner wall of the cylinder. It appears that a foreign object got stuck there.

I also got scratches on my VFC HK416CAG, and it seems that aluminum cylinders are made of a soft material and get scratched easily. I think it's probably one of the cheapest types of extruded aluminum, A2014, with a black anodized finish for decoration.

I think even 2000-series aluminum would be fine if you hard anodized or hard plated it... Or you could use 6000-series aluminum.

From now on, I will primarily use stainless steel or brass (copper alloys: depending on the alloy, copper can also be quite soft) cylinders.

I did a seal check with this cylinder and the piston, and it was OK, but I don't like it, so I'm going to replace it. The only one I have in stock is a full-size stainless steel cylinder from Laylax, so I'll modify it into an acceleration cylinder.

First, determine the position.

Carefully drill a hole using a rotary tool, making sure not to damage the inner diameter.

It's made of hard stainless steel, but with a powerful Dremel rotary tool and a tungsten bit, it only takes about 5 minutes. Finally, carefully smooth the cut surface and remove any burrs, and you're done.

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.

・Tungsten bit
It's the hardest and strongest metal, so you can process it easily. Please pay attention to the bit shank diameter. The bit shank diameter of the Amazon link is 3.00mm.

Now we'll assemble the gearbox.

Incidentally, the main spring had worn out, causing a drop in muzzle velocity, so I added two 2mm spacers to raise it by a total of 4mm.

This is the spacer.

Next, I changed the grip from the original to a PTS enhanced polymer grip, based on my personal preference.

I personally dislike the index finger protrusion on the standard A2 type grip (it hurts my finger), so I often replace it. Some people say this grip has an unfavorable motor angle, but I've never noticed any issues.

Also, brushless motors have a special end bell (the back of the motor) that sometimes requires modification, but this grip did not require any modification.

The lid shape does not interfere with anything.

There's too much space between the grip and the motor, causing the motor to rattle during operation. So, I used masking tape to eliminate the rattle.

Finally, one change from the previous setup is a slight modification to the wiring.

The goal was to improve battery storage, so I replaced the wiring between the fuse and connector inside the stock pipe with soft silicone-coated wiring (Eagle Model). The Teflon-coated wiring was too stiff and difficult to use.

Personally, I don't really see the need for Teflon coating, so lately I've been using 1.25 sq silicone-coated wire (from Eagle Model) for all my wiring.

This is completed.

Live-fire performance verification

We will now verify the actual firing performance.

The conditions were a room temperature of 22°C and the battery used was an ET-1 LiPo battery Red Line (equivalent to 35C) 1200mAh with a voltage of 8.2V.

I'm using VFC bio BBs (0.2g) and semi-automatic mode with a slight hop-up setting of about 15 out of 1.5.

It's quite accurate and looks good.

Introduction article on chronographs

Next is the full-auto rate of fire. Ideally, I would have liked to use the same chronograph, but the firing box was too small, and ricochets prevented me from taking measurements, so the results are from the Xcortech X3200 Mk3.

The rate of fire is 28.4 rounds per second and the muzzle velocity is also good, so it's perfect. With a full charge of 8.4V, it becomes 32 rounds per second, but I think feeding will be fine.

If you're interested, please also check out my review of the chronograph.

Incidentally, learning from past mistakes, I used a no-name magazine that I bought at Echigoya instead of a high-quality PTS PMAG for the test.

Regarding the trajectory, I don't think there will be any change as the hop-up chamber remains the same as last time.

Finally, here's a video of it in operation. The conditions are the same as for the muzzle velocity measurement.

VFC MK18 mod.1 AEG High Cycle Final Specification Semi-Auto

VFC MK18 mod.1 AEG, High Cycle, Final Specification, Full Auto

I think it's moving quite briskly.

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 and recipes

High-cycle recipe
With a 7.4V 1200mAh LiPo battery at 35C, it can fire 32 rounds per second with a muzzle velocity of around 95m/s (full auto with an 11.1V LiPo is not possible, but semi-auto is possible).

I think this should allow you to replicate it and achieve similar performance.

The VFC MK18 mod.1 doesn't have any special mechanisms or structures, so it should be almost identical to a typical Ver.2 gearbox. However, some modifications may be necessary, so please refer to the article for details.

Aside from the brushless motor, the rest of the setup is fairly standard.

VFC MK18 mod.1 AEG Full Metal Tan Color (Officially Licensed Version, JP Version)
This is the main article. It's also available in black in addition to tan.

The VFC Mk18 mod.1 has a 10.3-inch barrel, but the RIS2's 14.5-inch barrel is also cool and highly recommended.

VFC VR16 RISⅡ Daniel Defense
The engraving is different, and the internal components have been slightly upgraded. The link is for the 14.5-inch tan color.

About brushless motors (characteristics)

After using a brushless motor for a while and getting a feel for its quirks, I'll write down a few things that caught my attention.

Brushless motors have a control board attached to the end bell and are digitally controlled. Therefore, it seems to take about 1-2 seconds to start up after connecting the battery. So, it's okay if it doesn't start immediately.

Although I don't know the details, it monitors voltage, temperature, and overload, and automatically stops operating when it reaches its set thresholds. It also automatically stops working when the battery voltage drops low (I don't know the exact voltage), so it's not broken (I was surprised at first). It would be nice if it would notify you with vibration or sound before stopping, but it doesn't have such a function, so be careful.

Finally, regarding fuel efficiency, it doesn't seem to be very good. This might be due to the high load of the specifications I've built, but it barely runs on a 7.4V LiPo battery with a storage voltage of 7.6V.

In other words, because the motor requires a high amount of power when starting up, if the battery voltage is around 7.6V, it will momentarily enter the auto-stop zone and its operation will become unstable.

Therefore, I think the power consumption is high and the fuel efficiency is not good.

These are the points to be aware of.

Next, let's look at the advantages.

The advantage is that by customizing around this motor without using an FCU, you can achieve the same response as an FCU-equipped model (such as one with pre-cocking). It also inevitably results in a high rate of fire (even with a standard gear ratio of 18:1, it seems capable of around 22 rounds per second; a simple bolt-on installation would likely cause a crash).

For comparison, building a high-response custom setup with a brushless motor (1 yen) is likely to be cheaper than building one with an FCU and a high-spec motor (1 yen + 5 yen).

However, since it doesn't allow for fine control or adjustment (pre-cocking, cycle, burst, etc.), you should carefully consider when and where to use it (apparently, Option No.1 has recently released an FCU for brushless motors).

High-response, high-cycle custom builds generally involve an FCU + high-spec motor, a double sector (DSG) motor, or a brushless motor (either single or double sector). It's best to choose one that suits your purpose and budget (double sector motors are probably the cheapest but most challenging).

That concludes our high-cycle custom build using a brushless motor and a single sector gear.

Thank you for your company.