VFC AEG Mk18 mod1 High Cycle Custom: Chamber Edition

Continuing from last timeWe will proceed with the customization.

Since we finished preparing the parts inside the gearbox in the last step, let's start assembling them.

Continuing the assembly of the gearbox.

Close the gearbox, install AIRSOFT97's unequal pitch spring M100, and screw it in with the spring guide.

To prevent rattling, apply high-viscosity silicone grease (Tokyo Marui's high-viscosity grease) to the spring and Bell Hammer No. 2 to the spring guide.

Insert the gearbox into the receiver and attach the motor and grip.

Then, without assembling the stock pipe, I connected the battery and performed a test run. The test run results were excellent.

This completes the assembly of the gearbox.

Assembly of the hop-up chamber

I want to change the hop-up packing, so I'm going to disassemble the chamber.

The drum on the VFC's stock exhaust chamber is held in place by a circlip, making it a pain to remove. The structure and construction of the stock exhaust chamber itself seem good.

There are many small parts, so I will proceed carefully.

First, we'll file and modify the hop-up window on the inner barrel. The modification involves smoothing the front and back of the hop-up window so that the hop-up protrusion can descend more easily.

For details on modifying the hop-up window on the inner barrel, click here →I tried making my own G-HOP, Part 1: Production.

Next, we'll check the hop packing and hop cushion that will be installed.

As usual, apply Tokyo Marui high-viscosity grease to the hop-up mounting area of ​​the inner barrel, attach the hop-up packing, and insert the barrel into the chamber.

Maple Leaf hop packings are extremely tight when inserting them into the chamber, so be careful to install them without them shifting (Maple Leaf packings are often made on the larger side).

Also, the C-clip used to position the inner barrel is incredibly stiff.

Next, wrap masking tape around the tip of the inner barrel to prevent it from wobbling against the outer barrel.

Finally, check how the hop's protrusions are descending.

That looks good.

All that's left is to assemble it into the upper receiver and you're done.

When working with VFC chambers, be aware that circlips are used, so you will need the following tools.

Snap ring pliers set
I don't use it very often, but it's frustrating when it's needed and I don't have the right tools (it's often used in hop-up chambers). So having a cheap set is convenient.

Live firing verification

It's finally finished, and now it's time for a live-fire test. We'll measure the muzzle velocity with a chronograph.

20 m/s, 25 m/s... what?! (It was so shocking I didn't take any pictures.)

There's an air leak. It needs to be redone.

Let's consider the cause.

The only thing we couldn't confirm regarding airtightness was that the nozzle closing timing had changed, so we focused on that.

Addressing the decrease in initial velocity

I suspected that the increased cycle rate was preventing the nozzle from closing in time, so I decided to trim the vanes on the tappet plate.

I'll go with cutting off about the bottom third based on my intuition.

Also, if the edges are left unfinished, the nozzle's closing behavior will be disrupted, so we round the corners.

Before cutting

After cutting

This significantly speeds up the nozzle closing timing, which should improve airtightness.

Assemble and fire.

It hasn't changed at all.

Although it seemed unlikely, I suspected an air leak between the chamber and the nozzle.

Actually, it took me about 5 hours to get here.

I've been using Maple Leaf products up until now and have never experienced any air leaks from the gaskets, so I didn't suspect anything at all.

I was kind of hesitant to try anything, just as a last resort.

I've rebuilt the gearbox countless times up to this point.

Just like with the Chris Vector, I was trained to the point where I could assemble it at the speed of Forrest Gump.

I can't give up on the long-contact gasket, so I'll try installing a slim, 60-hardness long-contact gasket from Miyagawa Rubber, which has a similar opening to the original one, from my stock of gaskets.

Comparing the shape of the hop-up opening of the Maple Leaf hop-up with that of Miyagawa, Miyagawa's is slightly wider in diameter. The outer diameter is also just a little bit narrower. (Both the VFC genuine hop-up and the Tokyo Marui genuine hop-up are similar to Miyagawa's.)

Maple Leaf seems to have taken considerable care to ensure airtightness, narrowing the diameter at the opening while making the outer diameter larger.

I'll assemble it as usual.

Clean the hop-up window of the inner barrel a little.

Install the hop packing.

Assemble the hop chamber.

Check how the hop's protrusion descends.

I don't really like Miyagawa's packing because it's difficult to center, but I did my best.

We will install it and take measurements.

However, the variation in initial velocity was extreme.

Since I had no other choice, I tried several gaskets I had on hand, but none of them worked except for the genuine VFC ones.

But I can't give up on long-range photography.

Moreover, the fact that only genuine gaskets are acceptable is not very appealing.

think.

It seems that, although I'm not sure if it's just my unit, the distance between the nozzle and the gasket opening is extremely tight, and even a slight change in dimensions causes air leaks.

Furthermore, the spring that determines the position of the chamber is not very strong, so there is a possibility that the gearbox and the chamber are not in a tight seal.

Okay, I've decided to change the exhaust chamber. There are various types of exhaust chambers available, including those from Prowin.

After much deliberation, I chose a somewhat niche chamber.

This will be revealed next time!Customization continues.