I previously did two unboxing reviews of the UMAREX/VFC VP9 JP version.

This time, we'll be disassembling the slide while simultaneously showing you how to customize it.

Custom goals and parts procurement

To recap from last time, the goals of this custom build are as follows:

Since this project will mainly involve machining, I prepared only a few parts, just an inner barrel (which I had in stock at home).

This is a precision inner barrel from RA-TECH with an inner diameter of 6.02mm and a length of 97mm.

Ultimately, I ended up using plastic sheets and leftover flow valve springs, but basically, the main work involved modifications.

Let's start by disassembling the slide's blowback engine.

Slide blowback engine disassembly and customization

First, perform a field strip to remove each component.

Let's take a look at the back of the rear end of the slide.

Remove the two screws that secure the rear sight. Be careful, as there is a lot of threadlocker on them.

Although there are no photos, the rear sight can be removed by sliding it to the side.

Next, remove the screws from the extractor and the knocker return groove.

Now you can remove the blowback engine and extractor.

Now let's remove the front sight. The front sight is held in place by a hexagonal grub screw.

The front sight, like the rear sight, can be removed by sliding it to the side.

Here, let's compare the sight set and extractor included with the DX Special Combo.

genuine

DX Special Combo

The site is painted blue with phosphorescent paint, and since it's made of iron, it has a nice texture.

If you perform the steps in the reverse order of what has been described so far, you will have finished replacing the included parts.

Next, let's take a look at the blowback engine that we removed.

It comes with two nozzle return springs. This design ensures reliable operation.

Let's look at it from the side.

The silver knocker return groove is simply held in place by a series of interlocking grooves, so it can be easily removed.

Next, let's disassemble the nozzle.

Remove the screw and the nozzle return spring. The spring is only held in place by a hook, so you don't need to remove the screw.

Now you can disassemble all the parts of the blowback engine.

First, let's look at the piston section.

This piston has an unusual shape and a considerable surface area. While many large pistons these days are circular and boast a diameter of 15mm, this one is even larger.

面積では15mm径ピストンだと7.5×7.5×3.14=176.6mm^2に対し、本製品はおおよそ20×10=200mm^2（台形を正方形にしているので正確でない）で1.15倍くらい大きいので迫力あるブローバックを生み出しています。

Let's change direction and take a look at the piston.

The piston itself is made of resin and is quite lightweight, and it has been machined to remove as much material as possible. This is quite costly.

Also, at the top of the gun, there's a silver plate that lowers the hammer and a component for the cocking indicator. It's quite an elaborate mechanism.

Let's look at the other side.

Next, let's look at the flow valve from the back of the nozzle.

Actually, the screws were removed during disassembly, so they are already detached, but I've put them back in for observation purposes.

The flow valve is designed to stay firmly in place and not rotate.

I arranged all the disassembled parts of the blowback engine in the order they were installed.

Since I had some flow valve springs with different loads lying around, I'll assemble them while comparing them to the original ones.

The original springs are often short, with few coils, and are pitch springs, as is common with Tokyo Marui products, but this product came with a considerably longer spring.

It appears that the large forward movement of the flow valve allows the propellant gas to flow for a longer period, resulting in a larger gas output and thus a relatively high muzzle velocity.

The custom part on the right is Strike Arms' new Long Spring Medium (green), which I'll be trying out in this VP9.

Custom springs have a slightly higher load and longer free length than the stock springs, so I think they will slightly improve muzzle velocity and reduce fluctuations in muzzle velocity.

If you want to increase the initial velocity even more, I think adding washers or similar parts to increase the initial load will increase the initial velocity.

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

Finally, let's look at the flow valve.

Next, I lightly polish the slide rail section during the fitting process. I find using sandpaper tedious, so I use a rotary tool to buff it.

Both sides will be polished.

Next, apply Bell Hammer Gold No. 0 to the blowback engine parts and carefully assemble them. Incidentally, out of the box, the blowback engine parts have absolutely no grease applied (only a little silicone spray).

At the very least, applying something equivalent to Tokyo Marui's silicone grease, even if not Bellhammer, will improve its movement (Tokyo Marui uses it as standard).

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.

This is completed.

Let's take a look at the site that was included as a bonus. I forgot to take a picture of the extractor.

リアサイト

Front sight

Next, we'll disassemble and customize the barrel.

Outer barrel and hop-up chamber disassembly and customization

Let's look at the outer barrel from below. The outer barrel can be removed by removing the spring shown in the picture.

It slips right off towards the muzzle.

Looking at the tip of the outer barrel, it seems that in the past there were threads inside the muzzle, but mine didn't have them.

Instead, it featured rifling.

Next, we'll disassemble the hop-up chamber. You can disassemble it by removing the two screws shown in the picture.

Be careful not to lose the spring used to pull the outer barrel at this time.

Let's open the hop chamber and take a look.

This is a common type with a single-arm hop-up dial.

Let's take a look at each component.

This is a hop packing. It's a long-type with two points of contact, where the center of the protrusion is slightly indented.

This gasket seems to be well-made, so I'll use it as is.

Next is the hop arm.

This is a cantilevered arm with a two-point mounting system. I don't particularly like this type because, due to its cantilever design, it has low rigidity and can tilt due to the elasticity of the hop-up packing. Furthermore, even though the hop-up packing is a long-mount type, it cannot perform to its full potential with a two-point mounting system.

Therefore, it's custom-made.

To create a longer-hanging type, I inserted a 1mm thick plastic sheet and a piece of 0.5mm thick hop packing into the gap between the two hooks.

For now, I'll build it with these specifications.

Next, let's look at the inner barrel.

First up is the hop window. This is the type of window that is wide.

The tip has grooves around its outer circumference, and the inner diameter has a very long tapered finish, making it very beautifully made.

The length is 94.5mm, which is a rather odd size.

For some reason, the O-ring that was included with previous batches was missing. Presumably, they stopped including it because positioning the inner barrel relative to the movable outer barrel wouldn't be meaningful.

This barrel is of such high quality that you could use it as is, but I have a RA-TECH precision barrel with an inner diameter of 6.02mm and a length of 97mm on hand that looks like it will fit, so I'll try assembling it with that.

This is a comparison with the original part.

This is the hop window section.

The hop window is narrower, but it doesn't seem to be a problem.

Next is the tip of the barrel.

The custom part only had a chamfered edge. The original part is made of brass, while the custom part is probably made of stainless steel, which seems to be stronger and more rigid.

As usual, I lightly filed down the edge of the hop-up window on the custom barrel. Stainless steel is hard and a pain to work with.

There isn't much of a difference, but I always file it down because I don't like having burrs left over.

Now, we'll assemble it carefully.

Once the chamber is assembled, check how the hop-up protrusions are positioned.

Hop MAX

It's coming down nicely and straight. It's hard to see in the photo, but it's a proper long hop.

Next, we'll assemble the other parts.

Customization of the slide side is complete.

Here are the finished slides.

Apply Bellhammer Gold Grease No. 2 carefully with a brush to all moving and sliding parts, except for the internal components of the blowback engine.

In my case, I apply a little extra grease, manually move the part, and wipe off the excess to determine the right amount. It's a bit wasteful, but I use this method to ensure I'm applying the grease correctly.

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.

This is what the site I exchanged with looks like.

Incidentally, I lengthened the inner barrel by about 2.5mm, so now the outer barrel and inner barrel are exactly the same length (they're flush).

It's silver and stands out, so I think I'll paint it black with a marker later.

This completes the slide side.

Next time, I'll be showing you how to disassemble and customize the frame and trigger mechanism.

If you're interested, please join me.

Custom parts introduced this time

・RA-TECH 6.02mm Precision Inner Barrel, 97mm Length

It was only available from Strike Arms. However, I think the performance would be the same if the inner diameter is the same.

For reference, the original length is 94.5mm, so if you look for a Tokyo Marui Hi-CAPA 4.3 or USP with a length of 95mm, you can find one that's almost the same length. I wanted to increase the acceleration zone of the bullet as much as possible, so I went with the absolute maximum of 97mm.

・PDI Inner diameter 6.01mm Length 97mm
Since PDI is known for its high accuracy and reliability, their product might be even better than the one we initially chose.

・Maple Leaf Crazy Jet, 97mm in length
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.

The hop-up packing is quite good in its original form, so I think it's best to keep using it as is when making any modifications.

・UMAREX/VFC VP9 special comb DX/JP version
It comes with a steel extractor, a luminous sight set, and a slide takedown lever.

・UMAREX/VFC VP9 STD JP version
The extractor, sight, and lever are made of aluminum. The difference is purely cosmetic.

・Le Pair Magazine
It seems they've restocked, and the price is now reasonable. I recommend getting it while it's still in stock.

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