Tokyo Marui Glock 17 GNE4 Customization for Improved Functionality

I previously introduced a custom modification to the Tokyo Marui Glock 17 GEN4, which involved increasing the muzzle velocity and replacing the sights.

I finally got my hands on Guarder's lightweight aluminum breech for the Tokyo Marui Glock 17 GEN4, which I'd been eagerly awaiting, so this time I'll be showing you how to install it and its shooting performance.

Let's take a look at the lightweight breeches I acquired.

Guarder Lightweight Aluminum Breech

It's a package.

The original breech is made of zinc alloy and has a fair amount of weight, but this one is made of lightweight aluminum and weighs only 18g. I'll compare the actual weight when I disassemble it.

Let's take the contents out of the package and take a look.

The plain color of the alum is usually silver, but this one is painted black. The paint has a rough, powdery feel to it. It is probably powder coated.

These are accessories.

The package includes a backplate, screws for securing the breech, and a nozzle return spring.

I'm not entirely sure what the purpose of the backplate is, but I suspect the screws have been changed to a size suitable for aluminum, and the nozzle return spring is included to accommodate the increased slide speed.

The above is a list of the contents of the product.

Before assembling, please note that installing a lightweight breech like this product will improve operability and slide speed, but will also reduce the recoil force.

As with all customizations, I recommend incorporating them according to your own usage and preferences.

Disassembly and assembly

We will now disassemble it before reassembly.

As I mentioned in the previous custom build, I'll explain the procedure for rearranging the breeches, as I think there might be some people who are seeing this for the first time.

break down

Remove the slide using a field strip. The instructions for this are in the manual, so please refer to that.

Next, remove the recoil spring, barrel, and hop-up chamber from inside the slide.

I don't think you'll have any trouble with this step either.

Next, we'll remove the bleach.

Remove the screws that secure the breech. They are located near the back of the rear sight.

Even if you remove the screws, you cannot remove the breech.

This is fitted into the slide to precisely position the breech for improved blowback performance. Therefore, as shown in the next picture, you can remove it by spreading the ejection port to the left and right while pushing the nozzle downwards.

This step is a little tricky, but applying too much force at once can damage the slide or nozzle, so please remove it by applying force little by little.

Now the Bleach bottle itself will come out.

We will break this down further.

Remove the nozzle. It's simply fitted in place, so it comes off easily.

This is a bleach with the nozzle removed.

The breech has a rubber part called a piston cup, so remove it.

When you remove the piston cup, a screw will be exposed.

After removing this screw, there is a plastic part inside, so remove that as well.

This completely dissolves the bleach.

When the disassembled parts are laid out, they look like the following picture.

Here, let's compare the weight of the original zinc alloy breech with that of the aluminum breech.

Genuine zinc alloy part

Made of girder aluminum alloy

Garder's bleach comes in exactly 18g, just as advertised, which is amazing.

Incidentally, the specific gravity of zinc alloy is approximately 6.8 and that of aluminum alloy is approximately 2.7, so the ratio is as expected. This means that the weight ratio is correct, so the volume is about the same, and therefore the shape is almost identical. Therefore, it can be said that Guarder's breeches accurately reproduce the original shape.

Next, we'll assemble it. It's just the reverse of the disassembly process, so I'll briefly explain it.

Built-in

Garder's Bleach has no grease applied to it, so I'll apply some.

Applying grease is a matter of personal preference; some people prefer to use silicone oil spray to avoid attracting dust and dirt, so it really comes down to what you like. As a mechanical engineer, I prefer to avoid having sliding parts without lubrication, so I use grease.

As usual, the grease I'm using this time is Bellhammer Gold Grease No. 0.

Bellhammer No. 0 Gold Grease
This is a classic, top-quality grease. No. 0 is a low-viscosity grease. I generally use No. 0 for resin-to-resistance and resin-to-metal connections.

All that's left is to assemble it in the expected order.

Assemble the parts necessary for the breech.

Insert the bleach into the slide.

Assemble the remaining parts and it's complete.

Incidentally, I investigated how much the weight changed across the entire slide.

The difference is approximately 21.5g, or about 11% lighter, which should have a significant impact on performance.

Live-fire performance verification

We will test the shooting performance under the usual conditions.

Fill the magazine completely with HFC-134a gas and raise the magazine surface temperature to approximately 26°C. The room temperature is around 20°C.

I haven't modified anything that would affect the initial velocity, but I'll measure it anyway.

The test was conducted using G&G 0.2g bio BBs with the hop-up setting at 0.

Under similar conditions, hop gauge at MAX

The performance is lower than last time, probably due to the lower temperature, but it's still perfectly adequate.

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

Fuel efficiency

Next is fuel efficiency.

This is the weight of the magazine when it is full of gas.

This is the weight of a magazine after it has been empty (25 rounds).

The amount of gas consumed was 3.5g, which means that 0.14g was consumed per shot.

The original state consumed 0.33g (though the measurement is questionable), while the previous customized state consumed 0.3g, so it's been cut in half.

I believe this is a result of the slide becoming lighter and the slide speed increasing, which in turn resulted in faster gas cut-off.

Next is a video showing the operation.

Tokyo Marui Glock 17 GEN4 Lightweight Breech

It was already working quite well, but it's gotten even better.

Personally, what I'm most looking forward to is improved performance at low temperatures. I haven't compared them directly, but I think it's significantly better.

This is completed.

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, all I did this time was replace the breech with a lightweight one, so it was a simple job that should only take about 20 minutes.

Moreover, it's a fantastic product that delivers reliable results with no modifications required and a simple plug-and-play installation.

・Guarder Lightweight Aluminum Breech
I've always relied on this long-established lightweight bleach brand. I've never had any problems with it.
Please note that this product is specifically designed for Glock 17 and 19 GEN4 models and cannot be attached to other models (GEN3 is an exception).

It was available at several stores in Akihabara.

This completes the internal customization of the Tokyo Marui Glock 17 GEN4.

By the way, my go-to customizations for Tokyo Marui gas blowback pistols usually involve the following:

Tokyo Marui guns perform quite well right out of the box, but applying the above modifications increases the muzzle velocity by approximately 5 m/s, the muzzle velocity remains unchanged even with hop-up applied (a slight increase in velocity), and fuel efficiency improves by about 30%.

In return, the hop-up adjustment becomes more sensitive and the recoil feels lighter.

Since I use it for airsoft games, I'm aiming to increase the range and improve its performance, so I'm doing things like this.

Thank you for your time.

・Tokyo Marui Glock 17 GEN4 Gas Blowback
It has amazing performance and I highly recommend it.

・Tokyo Marui Glock 17 Common Spare Magazine
I'm so happy that the magazines are cheaper compared to other companies.