UMAREX/VFC GLOCK19X Customization: Increased muzzle velocity and improved durability

Last time, I did a review of the UMAREX/VFC GLOCK19X, which was almost straight out of the box.

It's a pretty good product, but there are a few things that bother me, so this time I'll be customizing it with the aim of improving those aspects.

We'll refine this area.

Slide disassembly and customization

First, remove the slide. Before removing the slide, pull it back to lower the hammer.

Then, while lowering the lever located in front of the slide stop lever, pull the slide forward to remove it. By the way, the lever is quite stiff.

Here are the slides.

The recoil spring and outer barrel are simply fitted in place, so remove them.

A resin part for shock absorption was attached to the front of the recoil spring assembly.

This is the outer barrel.

Blowback engine

Next, we'll remove the gas blowback engine.

It is secured by a single screw at the rear end of the slide.

The blowback engine can be easily removed by unscrewing it.

A blowback engine viewed from the side.

It's marked "G18CV2". It's probably using parts shared with the Glock 18C.

If you release the spring hook here, the resin part (nozzle) will come off.

This completes the assembly of the piston cup (the part that receives the gas pressure for the blowback), the flow valve (the part that switches between firing the bullet and blowback), the extractor, and the rear plate.

The part that receives gas pressure (piston cup)

Components that switch between firing bullets and blowback (such as flow valves and valve springs)

extractor

Should I call it a backplate?

The rubber part that receives the gas pressure (piston cup) has an amazing shape. Its large surface area suggests it will provide good blowback.

Let's take a look at the nozzle. It looks like it has a snail-like shape, which is good.

Now, we'll disassemble the part shown in the photo above that switches between firing and blowback.

There's a pin inserted from the side, so remove it. Once you remove the pin, the flow valve and spring will come out. These control the switching mechanism.

The image shows a custom spring. The flow valve has an anti-rotation design, which is a good shape that allows for stable gas switching.

The original spring is shown in the next picture.

Strengthening this spring will increase the muzzle velocity, but it will decrease fuel efficiency. However, if the spring is too strong, the gas route cannot be switched, and blowback will not occur.

Also, be careful when adjusting the initial velocity, as the gas temperature will affect the result.

You can get springs with different loads from Strike Arms, but if you change them, you need to be careful and consider the balance, otherwise you'll mess it up (you can always put it back to the original).

Alternatively, if you can find a spring of similar dimensions at a home improvement store, that will work too.

If you change the spring, adjust it while measuring the magazine temperature with a non-contact thermometer, and make sure it never exceeds 0.98J at an ambient temperature of 35℃.

・non-contact thermometer
It's essential for customizing gas guns.

All that's left is to apply silicone oil to each part using silicone spray and reassemble it. By the way, I recommend KSC's silicone spray; it's large, inexpensive, and a must-have for working on gas guns.

Silicone grease is applied only to the outer circumference of the rubber parts that receive gas pressure.

KSC Genuine New Gun Oil 430ml
Any silicone spray will do, but KSC's is convenient because it comes in a large size.

AZ Silicone Grease
This is a standard product from AZ. While Tokyo Marui's genuine grease is sufficient, the quantity is small, so AZ is recommended. It's also inexpensive.

Basically, with gas blowback guns, you can adjust the muzzle velocity by changing the shape of the spring and flow valve. If the muzzle velocity is too high, change to a weaker spring, and vice versa. The N-PAS also uses this principle.

That concludes the explanation of the blowback engine.

If you're interested, I've included an explanation of the gas blowback mechanism, so please take a look.

Barrel, hop chamber

Next, pry and pull the hop-up chamber out of the outer barrel, and the chamber will come off.

It's not held together by screws or anything like that; it's like a puzzle and quite difficult.

The photo shows the gun with a different barrel already installed. (Maple Leaf's Crazy Jet barrel)

Removing the two screws reveals the hop-up packing and hop-up adjustment mechanism. A silver, seesaw-like part adjusts the hop-up by moving a ring shaped like a mouth. That's a pretty clever idea.

By the way, the black inner barrel in the photo is the original part.

Looking at each part, first there's the gasket. A flat, long-type gasket seems suitable.

This is the part that presses against the packing. Unlike Marui's single-arm design, this one is double-arm, so it has a good shape that prevents it from tilting even when strong hop-up is applied.

Now, let's change the inner barrel. Both the genuine and aftermarket barrels have some burrs around the hop-up window, so it's recommended to remove them to prevent damage to the hop-up packing.

The edges can sometimes be so sharp they could cut your hand, so round them off.

Before processing

After processing.

I think simply lightly rubbing it with a round diamond file should be sufficient.

Diamond file set
These diamond files offer great value for money. The round files, in particular, are very useful. The 5-piece set is highly recommended.

My favorite inner barrel is the Crazy Jet Barrel from Maple Leaf. I don't really believe in the "jet effect" of this product, but I choose it because it seems to be of good quality.

In the case of gas guns, changing the barrel bore diameter significantly affects the muzzle velocity, so sometimes simply changing the barrel bore diameter is enough to increase the muzzle velocity. This eliminates the need to disassemble the blowback engine, and fuel consumption remains unchanged.

The Glock 19X is 84mm long.

• MAPLE LEAF Crazy Jet Barrel 84mm
This is a barrel I often use in gas blowback guns. I'm not sure about the jet effect, but it's a well-made barrel overall.

Normally, I would install the company's hop-up packing in this, but in my case, the packing was too big to fit in the chamber, so I decided to use the genuine part.

Finally, we'll modify the part that presses the hop-up packing. Since the hop-up amount is a bit low, we'll add some padding to the part that presses the packing. This time, we attached a piece of Marui's hop-up packing with adhesive.

This can also be used with other manufacturers' products to adjust the hop-up amount or extend the hop-up duration. For example, you can cover a genuine Marui hop-up rubber with heat-shrink tubing.

The rest is the same as with electric guns: apply Marui high-viscosity grease to the barrel and install the packing.

Check the hop-up's protrusion, then insert it into the outer barrel and you're done. Looks good.

Finally, before assembling the parts into the slide, lightly polish the sliding surface of the slide with #1000 grit sandpaper, then assemble the parts to complete the process.

Hammer, around the shear

Next, we'll address the issue of the hammer.

Since I don't use high-pressure gas, the hammer, sear, and knocker only need to be able to withstand the pressure of domestic alternative refrigerants (HFC-134a), so I'll replace them with hammer springs and knocker springs equivalent to those of Marui genuine parts.

Replacing the hammer spring and knocker spring with Tokyo Marui equivalent parts reduces the risk of excessive muzzle velocity because the knocker won't be able to strike the valve when the temperature rises and the gas pressure increases.

Furthermore, reducing the load will lessen the stress on the parts and improve their durability, so it is highly recommended.

If I had the parts, I could also replace it with a hammer machined from iron, but since I don't use high-pressure gas, I won't adopt that approach for cost reasons.

・AIP Inner Spring Set
I think any manufacturer is fine. Anything that's equivalent to Tokyo Marui's Glock load would be okay.

Now, remove the hammer assembly from the main body. Remove the pin shown in the picture.

By the way, I absolutely hate this task. I've done it on other models too, but the springs are stiff and it's difficult, parts fly off, and it's just awful (I'd rather not do it at all).

The direction is from left to right, as shown in the picture.

Next, the trigger bar and sear are connected, so we'll detach them. They come off easily.

This will allow you to remove the hammer assembly upwards. The spring that returns the knocker will also come off, so be careful not to lose it.

It's difficult to explain the hammer assembly process in words, so if anyone is going to try it, I highly recommend taking pictures before you disassemble it.

I'll include the necessary photos so that they can be incorporated into this site.

I took photos from the back and from above.

Rear

Photo from above

If you suddenly disassemble it here, the spring will fly out and cause trouble, so remove the shaft while inserting a pin punch.

Photo taken from the back

Assemble the spring by carefully shifting the pin punch to avoid scattering the parts.

This is after the replacement. The spring diameter is clearly different.

It feels like the load has decreased by about 50%.

The stock spring is way too strong. Even dry firing it feels like it's going to damage the hammer assembly. So, I recommend (almost essential) replacing the spring, even for those who just use it indoors.

Finally, apply Bellhammer No. 2 grease to the moving parts and assemble them into the main body to finish. If you don't like grease attracting dust, you can use silicone spray instead.

Since I prioritize smooth operation, I apply Bell Hammer lubricant. By the way, I also apply it to the sliding parts of the slide and frame.

By the way, I've written a detailed explanation of how to disassemble the entire gun, including the hammer unit, here, so please take a look if you're interested. It's basically the same as the company's G45.

Detailed instructions on how to assemble the hammer unit are available here, so please take a look if you're interested.

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.

I've written down the working principles of this rather confusing hammer, trigger, and magazine. Please take a look if you're interested.

Live firing verification

We will try to recreate the same conditions as during the review as much as possible.

The magazine is nearly full of gas, the surface temperature is set to about 27°C, and 22 rounds of Tokyo Marui Bio 0.2g BBs are used for the measurement, with a rate of 2 rounds per second.

The hop gauge is at 0.

Initial velocity when the first shot is close to the first shot

The initial velocity at almost the end of firing.

We were able to increase the initial velocity by approximately 4 m/s.

Well, since the barrel length is 84mm, I think this is about the limit.

The only option left is to extend the barrel, but that would defeat the purpose of a compact model, so I won't do that.

Also, because the gas output is relatively high relative to the barrel length, the muzzle velocity will increase when hop-up is applied.

With 0.2g BBs and the appropriate hop-up setting, it shoots around 75m/s, which I think is excellent for a gas blowback pistol of this size.

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

Live firing video (no ammunition loaded)

VFC GLOCK 19X Custom - Caution: Sound

I can't really tell since I can't compare them numerically, but did it make you feel better?

It's finally finished.

Complete

Since the exterior hasn't changed at all, this is purely for my own satisfaction.

I lined up Tokyo Marui's Glock 19 and Glock 17 GEN4 for comparison.

By the way, my S&T light didn't fit. The same goes for the Marui one. But it did fit on the rail of a long gun, so maybe it's a unique size for Glocks?

Finally, a photo with 9mm dummy cartridges and magazines.

I bought too many magazines. The original plus two extras would have been enough.

Summary

This is the first time I've introduced a gas blowback pistol in detail on this blog, so I've tried to explain everything thoroughly.

This post covers almost the entire scope of my gas blowback customization (I forgot to mention replacing the gas inlet).

Other modifications you can make include canceling the short recoil and enlarging and adjusting the position of the magazine's valve hole (simply changing the valve hole diameter won't change the muzzle velocity; it might slightly improve the feel of the blowback).

If there is demand, I will also introduce magazine customization.

In the case of gas blowback handguns, even if you work on them, the changes due to outside temperature are more significant, and since they're not meant to be your main weapon, you might wonder if it's worth going to such lengths, but it's really a matter of personal preference (long guns are a different story).

But it will definitely be better than doing nothing.

I hope this will be helpful to anyone who is thinking about doing it (I think it's a good idea to try things that improve durability).

That concludes my introduction to the UMAREX/VFC GLOCK 19X. It's a pretty good product, but I think you should change the hammer spring.

Afterwards, I checked the ballistics.

・UMAREX/VFC GLOCK19X GBB
I highly recommend it; it's ready to use right out of the box. What's even better is that the price is comparable to or even lower than domestic brands.

・Le Pair Magazine
The magazines are a bit more expensive compared to domestic ones.

・Injection valve for domestic gases
I recommend it (but be sure to use genuine O-rings).