In the previous disassembly of the WE Dragunov SVD, I was able to disassemble most of the parts.

This time, we'll proceed with disassembling and customizing the remaining part: the recoil spring.

Disassembly of the recoil spring

The recoil spring is located on the top cover. It consists of two springs, one at the muzzle and one at the stock.

Let's take this apart. There are about two pins at the rear end of the top cover, so let's take that apart.

The thinner pin is extremely stiff, so try your best to remove it.

The recoil spring unit can be removed from the top cover.

Next, remove the pin located at the rear end of the recoil spring unit.

This will result in the following picture, and you can then remove the spring.

We've now managed to disassemble most of the parts.

Custom

Around the bolts

We'll now assemble the parts around the bolt.

This involves replacing the flow valve spring inside the blowback engine to increase the amount of gas delivered to the firing side. The photos show the difference in load between the original spring and the flow valve spring from Strike Arms, as well as a comparison between a yellow and an unpainted spring.

Compared to the original, the spring length is longer and the load is higher, so the amount of gas released by the firing side increases. First, we'll assemble the yellow part.

Next, assemble the parts while applying Bellhammer Gold No. 0 grease to the sliding surfaces.

Apply grease to the sliding parts of the bolts (indicated by the yellow marker).

Applying grease to this area is a matter of personal preference. If you're concerned about dust accumulating, silicone spray might be a good alternative.

However, using grease definitely improves the movement.

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.

The bolt is now complete.

Incidentally, I had planned to change the gas cut timing to retract the valve knocker by reducing the amount of gas discharged in order to improve fuel efficiency, but upon inspecting the bolts, I found that the manufacturer had already taken measures by adding a sliding mold to the mold. After checking on my end, it seemed that there was no unnecessary gas discharge, so I decided not to touch it this time.

I've written about the operating principle of gas blowback guns, specifically focusing on the slide and bolt.

Recoil spring replacement

Next, we will replace the recoil spring.

The original springs are stiff and short, and are probably designed for use with high-pressure gases overseas, so I will replace them with softer, longer springs.

The springs I'll be using are Strike Arms' original blue and green ones.

Now, reassemble this onto the top cover. You'll notice that the spring is considerably longer.

This completes the recoil spring replacement.

Inner barrel and hop-up packing replacement

Next, we'll replace the inner barrel, which is the main feature of this product.

The inner barrel we'll be using this time consists of two separate pieces: a 250mm section with an inner diameter of 6.06mm and the remaining 350mm section with an inner diameter of 7.5mm. We'll assemble them together.

It's a snap-fit ​​design, and in my experience, the hole-to-shaft ratio is H8-h8 or H9-h9, which is a standard fit with decent precision. I'll also glue it to prevent it from coming loose.

Looking at the crucial hop window, it was smoothly machined and looked like a very good shape, so I decided not to modify it this time. However, I did slightly round off the edges with a round file.

Since we're at it, let's compare its length to the original.

Next, wrap masking tape around the middle of the barrel's length to prevent wobbling with the outer barrel, and then assemble it.

Insert the barrel from the muzzle end, the reverse of the assembly process.

Next, we'll assemble the hop packing and chamber. This time, we'll use Maple Leaf Macaron hops with a Delta hardness of 50.

As usual, I applied Tokyo Marui high-viscosity grease to the parts of the barrel other than the hop-up window, installed the packing, and secured it with sealing tape to ensure airtightness.

Next, I'll assemble Maple Leaf's Omega Cushion Rubber and the chamber assembly. This packing has a ring where the nozzle goes in to ensure airtightness, and if it's not a good fit, the nozzle will get stuck, so I'll check that.

The nozzle doesn't seem to be getting stuck in the packing, so the barrel assembly is now complete.

Polishing and greasing of parts

Next, we will polish and grease the sliding parts. We will basically use Bellhammer Gold No. 2.

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 greasing the area around the knocker. By the way, the screw that holds the spring that returns the knocker tends to loosen, so tighten it securely using threadlocker.

Next, lightly buff and polish the sliding surfaces of the receiver and bolt.

Next, assemble the trigger mechanism and apply grease.

All that's left is to reassemble it in the reverse order of disassembly, and you're done.

I've written an article about the operating principles of gas blowback guns, specifically focusing on the trigger, hammer, and magazine.

Live-fire performance verification

We will verify the actual firing performance.

The conditions were: ambient temperature around 25°C, half a magazine filled with HFC-134a gas, and S&T's 0.2g bio BBs.

I checked the hops by multiplying by approximately $ \frac{1}{3}$ on the scale.

I don't have a photo, but it was stable at around 90 m/s. I was prepared to do some fine-tuning around the flow valve, but it went surprisingly smoothly.

However, after firing about one magazine, the incident occurred.

The hop-up arm on the hop-up chamber broke.

In addition to the original dimensions being somewhat inaccurate, it seems it broke because it couldn't withstand the resilience of Maple Leaf's hop packing.

I was so surprised by this that I forgot to take a picture of the chronograph.

As a solution, I tried gluing it together and reinforcing it with a 1mm plastic sheet, but it didn't work.

There's nothing else to do but order the parts and wait.

For reference, I've attached a video demonstrating the blowback mechanism.

WE SVD GBB Custom

I think the movement itself has become much sharper. And yet, the feeling of recoil weight remains exactly the same.

I haven't been able to measure the fuel efficiency due to a hop-up issue, but it should probably be better.

I will update this page once the parts arrive.

Ultimately, I settled on Omega Cushion Rubber and the original hop-up packing for the hop-up system.

Summary

I'm waiting for parts, but I'll put it all together for now.

The parts used this time are as follows:

Maple Leaf Omega Action Rubber
It works quite well when combined with a flat hop-up. Although it's labeled for electric airsoft guns, it can be installed in the hop-up chamber of Tokyo Marui M4 series guns.

・Strike Arms' original SVD recoil spring (blue)

・Strike Arms' original SVD recoil spring (green)

・Strike Arms Flow Valve Spring (Yellow)

・Strike Arms x KM Planning Collaboration TN Barrel Large Bore + Extension Pipe Specification 600mm (Base Length 250mm)

will be important.

The rest was polishing and greasing based on my intuition, followed by careful assembly.

My impression is that the dimensions of each part were quite tight, requiring considerable force for maintenance. Furthermore, some parts were secured with threadlocker in unusual places, making disassembly quite difficult.

Also, although the barrel is shorter in this batch, it is still 350mm long, and I think the unstable muzzle velocity was due to an imbalance between gas release and barrel volume (the flow valve spring was too soft).

Furthermore, the stock recoil spring is short and stiff, so the bolt moves slowly, and the spring extends completely before it fully returns to its original position, resulting in a somewhat unsatisfactory movement.

It's definitely better to use a softer, longer spring and let it press down on the bolt until it's securely closed; this will improve the movement.

I'm currently waiting for parts, but I've summarized everything up to this point. I will update this as soon as the parts arrive.

WE-tech SVD Dragunov Aluminum Frame, Polymer Stock, Handguard
This is the Dragunov featured in this article.

WE-tech SVD Dragunov Aluminum Frame, Faux Wood Stock, Handguard
This is a fake wood version of the Dragunov featured in this article.

WE-tech SVD Dragunov Magazine
This is a spare magazine.