LAYLAX SIGSAUER M17 CO2 GBB Customization Completed (P320)

In the previous post, "LAYLAX SIGAIR Proforce M17 CO2 GBB Customization and Adjustment Part 1 (SIG P320)," we completed roughly half of the adjustments.

This time, we'll go through the process from customizing the blowback unit to its completion.

Adjusting the blowback unit

Now we'll make some adjustments to slightly increase the initial velocity.

The part to be machined is an orifice (aperture) for limiting the initial velocity.

The hole at the back.

Front hole

Removing this part alone will increase the initial velocity, but it will probably exceed the limit by a significant margin, so you should absolutely not remove it.

We'll enlarge this hole with a pin vise. Considering the thickness of the part, the maximum hole diameter we can drill is 3mm (leaving 0.7-1mm of wall thickness), so we'll use a 3mm vise.

• Pin vise
I think anything cheap will do. Since the material we're working with this time is soft plastic, it'll be fine as long as the diameter is right.

Using only a pin vise will leave burrs in the hole, so as a finishing touch, use a rotary tool to lightly shave the edges of the hole.

After processing, it turned out looking like this.

Rear hole (after processing)

Front hole (after processing)

We will measure the hole diameter for confirmation.

This is the tip.

This is the rear end.

I made the hole slightly wider at the rear end to regulate the gas flow.

Assemble this into the nozzle.

Next, we'll assemble the flow valve and spring.

It probably depends on the person, but I apply Bellhammer No. 0 Gold Grease to these parts before assembling them into the loading nozzle. My reasoning is that I believe a quicker flow valve movement prevents unnecessary gas release (preventing unnecessary gas from being released into the barrel).

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.

I accidentally filed down the nozzle here to disassemble it, so I'll fix it with putty. If I had carefully filed it down with minimal modification during disassembly, I don't think this fix would have been necessary.

Any putty will do, but I'll use Cemedyne resin putty, which happened to be sold at a nearby home improvement store.

Cemedyne Epoxy Putty for Plastics
Anything for resin should be fine. You might not even need to make any modifications.

I'll use this to make it look better.

Incidentally, to ensure the nozzle can be disassembled again, we'll add some material so that the pin that secures the floating valve isn't buried. It should be just enough to allow you to grip the pin with pliers.

Next, let's take a look at Bleach.

The sliding parts of the breech components have a rough surface due to the casting process.

I'll start buffing it with a rotary tool, just like always.

Dremel High-Speed ​​Rotary 4000
This is my go-to rotary tool that I always use. Having this expands the possibilities of your DIY projects. There are two popular models, the 3000 and the 4000, but I recommend the 4000 because it comes with a set of tools and has more power.

This is after buffing.

This process is also carried out carefully, taking care not to overdo it, as this could lead to excessive dimensional changes and compromise the original function.

Next, I'll assemble it while applying Bellhammer No. 0 Gold Grease.

Just incorporate this into your slides and you're done.

What I noticed here was that the thread engagement for the screws that secure the breech, plate, and rear sight seemed rather short.

Normally, the thread engagement of a screw in iron requires about 1.5 to 2 times the screw diameter (at least 9mm for a 6mm screw), but it felt shorter than that. Therefore, you should be careful when mounting heavy objects like red dot sights, as they might break due to inertia.

Next is the recoil spring.

This simply involves applying grease to the rod section.

I happened to notice before assembling it that the outer barrel wasn't securely fixed.

This part is moving too much and seems to be affecting accuracy, so I'll make some adjustments.

First, let's look at the positioning mechanism here.

The positioning is achieved by interlocking the protrusions and indentations. Therefore, we will make adjustments in another part without touching the protruding parts.

This is a simple surface, so I'll fix it by attaching a plastic sheet. I'll attach a 0.2mm plastic sheet by feel.

Now we'll do a test assembly and check it.

There's a bit of looseness, but considering ease of assembly and the potential for misalignment of the sight's aiming point, it wouldn't be good if it were too tight, so I'll leave it as is.

All that's left is to assemble the slide assembly, apply Bellhammer No. 2 Gold Grease to the sliding parts, and it's finished.

Tamiya plastic sheet, 0.2mm thick
There's no particular reason, but I use Tamiya plastic sheets. 0.2mm is a convenient thickness for filling small gaps and adjusting thickness.

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.

Initial velocity measurement and correction

We'll measure the initial velocity as usual.

The conditions are as follows: magazine temperature 26℃, room temperature 22℃, using 0.2g bio BBs.

This is the initial velocity.

The initial velocity is clearly too high, so we will adjust it.

There are various ways to reduce muzzle velocity, such as cutting the barrel, drilling holes in the nozzle, or narrowing the nozzle hole, but the method I used here to reduce muzzle velocity was to cut the flow valve spring (which is easy to do and cannot be reversed, so I think it's legally acceptable).

I've previously explained the gas flow in gas blowback guns, so please take a look if you're interested. After reading it, you'll be able to adjust the muzzle velocity of any GBB (Gas Blowback) gun.

Disassemble the nozzle again and remove the flow valve and spring.

I'm going to cut this spring. First, I cut off about 2.5 turns by feel.

We'll temporarily assemble this into the flow valve.

It's hard to even call it a spring anymore, but it works, so I'll assemble it like this. As a designer, I'm hesitant about a spring without a seat coil, but there's no other way.

This significantly lowers the position of the flow valve, greatly reducing the gas flow rate that determines the muzzle velocity. If you mess up cutting the spring here, you can just buy a suitable flow valve spring from the market and try again. It's probably the same size as a typical gas blowback pistol like Tokyo Marui's Glock.

Perhaps the weakest flow valve spring sold by Strike Arms might be just right.

Reassemble it once more and it's complete.

Live-fire performance verification

As usual, we will now check the actual firing performance.

The conditions were that the gas tank was almost full, the magazine surface temperature was 26.6°C, and the room temperature was around 22°C.

The BBs used are VFC 0.2g bio BBs, and the hop-up setting is 0. The BBs falling out issue has been resolved, so it can now be fired normally.

These are the initial velocities of several shots fired.

It's around 81-85 m/s, which is good.

I think this brings it down to the average muzzle velocity of a CO2 gas blowback rifle (80-85 m/s at 25°C).

To ensure compliance with regulations, the magazine surface temperature was heated to above 35°C to confirm that the reading was within the legal limit of 0.989J at 35°C.

Now we'll measure the initial velocity in the same way.

I was relieved because it was within the regulations.

These are the initial velocities of several shots fired.

I knew the temperature would drop each time I fired because the room temperature was 22℃, but I did it just to check for variations, and it was fine.

Based on these results, if you're using CO2, I think it's probably not suitable unless you adjust both the rifle and handgun to 80-85 m/s with 0.2g BBs at a temperature of 26°C.

If anyone is planning to customize their vehicle, please use this as a reference.

Introduction article on chronographs

・Non-contact thermometer
I think this is an essential item for gas blowback customization. Anything cheap will do, though.

Fuel efficiency, operation video

Next is fuel efficiency.

We measure the magazine weight before firing.

We will measure the weight of this magazine after it has fired all 21 rounds.

With 21 shots, 3g of BBs were consumed, meaning the fuel efficiency is 0.143g per shot. This is a slight decrease from the 0.134g consumption out of the box.

A single CO4 cylinder holds approximately 12g, so theoretically you should be able to fire about four magazines. However, in reality, due to the reduction in thickness resulting from the decrease in volume, I think 3.5 magazines is a more realistic estimate.

That means one cylinder can fire about 70 shots, so I wouldn't say it's particularly fuel-efficient among CO2 guns (it's about average).

Next is a video of the operation (the conditions are almost the same as for the initial velocity measurement).

LAYLAX SIGAIR Proforce M17 CO2 GBB after adjustment

The slide speed was already fast, but after adjusting it, it became so fast that the camera couldn't even capture it. It's great!

This is before adjustments (under almost the same conditions).

LAYLAX SIGAIR Proforce M17 CO2 GBB (Out of Box)

It performs quite well right out of the box.

After correcting the Kure assembly inside the hop-up chamber and applying grease, the movement improved, making it easy to adjust the hop-up without using the included tools.

Next, I'd like to check the trajectory, but I don't have a large enough space, so I'll update this after I've checked it during an airsoft game.

This completes the customization and adjustments.

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

I managed to resolve almost all of the following issues through DIY alone. Therefore, there's no usual list of parts used in this summary. It's just a matter of effort (it might be tough if you don't have the right tools).

Simply following the basics of machinery—polishing the sliding parts and applying grease—can make a significant difference. While I used a rotary tool for polishing, which can be expensive to purchase, you can do it with sandpaper if you're patient. Other tools aren't expensive and are common items, so you should be able to manage.

To put it simply, if you have a screwdriver, wire cutters, sandpaper, grease, and patience, you can probably make something similar.

One important point to note is adjusting the initial velocity. CO2, or carbon dioxide, has a pressure of 6 MPa (at 25°C) compared to the conventional HFC-134a pressure of 660-700 kPa (at 25°C), which is about 10 times higher, so it is dangerous if not handled carefully.

I previously did strength calculations for a dangerous CO2 magazine, so please feel free to refer to them if you're interested.

Be careful, because if you handle it with the same mindset as you would with HFC-134a, you'll quickly reach a level that violates regulations.

I specifically increased the diameter of the orifice hole for adjusting the initial velocity from 2mm to 3mm in one go, but I think a hole diameter of around 2.3-2.4mm is more appropriate. Since it's easy to increase the initial velocity, it's absolutely crucial to stay within legal limits.

It performs quite well right out of the box, but with a few tweaks, it can be significantly improved, so I hope this will be helpful for anyone who is dissatisfied (it has high potential).

Thank you so much for sticking with me this far.

LAYLAX SIGAIR Proforce M17 CO2 GBB Coyote Brown
It's a good product despite some shortcomings. Furthermore, it's valuable because this is the only model officially adopted by the US military.

LAYLAX SIGAIR Proforce M17 CO2 GBB Spare Magazine
Since it's from LAYLAX, I think the supply will be stable, but given the current situation, there might not be any ships available, so I recommend buying while you can.

LAYLAX High Bullet CO2 Gas 6-Pack
Six bottles will probably be gone in no time, but I'll introduce them anyway.

LAYLAX High Bullet CO2 Gas 30-Pack
Since you'll be using them anyway, I recommend the 30-pack, which is cheaper. It's under 3000 yen, so it's a good deal.

Marushin CO2 Gas, 30-pack
It's probably usable. I think Marushin offers the best balance of price and quality.