Maruzen CA870 Charger Old Hop-Up Disassembly and Customization

In the last installment, we checked the appearance and performance of the Maruzen CA870 Charger, so this time we'll disassemble it and customize it.

Later, disassemble itIt appears this product is the old HOP version. The old HOP version was likely discontinued in 2014, so most people probably already own the NEW HOP version. Those considering purchasing should be aware that unless you're looking for a very old used product, only the NEW HOP version is available; the old HOP version is not sold.

I've reviewed, disassembled, and customized the NEW HOP version, so if you're interested in the NEW HOP version, please follow the link.

Let's get started and take it apart.

break down

First, to disassemble the outer barrel, remove the tip of the shotgun shell tube.

Next, remove the outer barrel. It's not fixed in place, so it will come right off.

Next, remove the grip.

The grip is only held in place by a screw inside, so it can be easily removed by unscrewing it. Note that removing the grip is not necessary to disassemble the main body.

The grip mounting area is similar to that of a gas blowback M4. It might be possible to attach a grip designed for a gas blowback rifle.

Next, remove the stock.

First, remove the stock and unscrew the screw at the base of the buffer tube.

It was quite loose, so I'll apply threadlocker when I assemble it.

The stock and grip attachment points can be removed.

Next, remove the hexagonal bolts on both sides of the main unit.

Be careful, as there is a pin in the hexagonal bolt hole on the right side of the photo.

Remove this pin using a punch and a maintenance stand.

You can use a pin punch from a 100-yen store, but I recommend one made by Signet.

Signet Pin Punch Set
It's not a luxury brand, but it's a recommended mid-range brand in the automotive industry that offers good value for money. Plus, it's inexpensive.

Eagle Force Maintenance Bench Block for Handguns
It's incredibly convenient to have. Moreover, it's designed for handguns but can also handle longer firearms, making it very useful. In fact, I personally didn't see the need for their M4 version.

Vessel Plastic Hammer
It's inexpensive, sturdy, and long-lasting. For a good balance of control and power, the 1-pound size is recommended.

Next, remove the trigger guard. It's just clipped in, so it comes off easily.

Next, you can remove the main unit and receiver cover. Remove them while wiggling them as they may catch on the trigger.

The main body and receiver have levers, springs, pin retaining clips, and bolt covers on both sides, so remove them to avoid losing them.

Lever and spring

Next, move to the front and remove the shot cell tube. It's secured with a screw at the base, so you can remove it by turning the tube counterclockwise.

Now, remove the outer barrel base, which is often forgotten during removal.

Now the entire exterior has been disassembled.

Next, we will disassemble the receiver. The receiver is fastened with four Torx T0.8 screws and spring pins.

Next, you can disassemble it by removing the pump action bar and opening it up. Be careful not to lose the hop-up adjustment parts, as they tend to come loose at this point.

Here's the shocking truth: it was the old hop version! I was shocked because I had already purchased Miyagawa Rubber's Hanamaru-kun hop packing for the CA870.

Next, let's look at the main components inside the receiver.

Main components inside the receiver

This is the rear end of the receiver. There's absolutely no grease applied except to the sear. Is this okay?

Next is the trigger. It does have grease applied to it, but it's some kind of dirty, mysterious grease.

　

Next is the shear. This one has absolutely no grease applied to it.

Next is the piston, which also has absolutely no grease applied to it. It also has an interesting diamond-shaped cross-section, which is probably a modification to prevent the use of wire-type or large-diameter, strong springs.

Next is the cylinder. This also has absolutely no grease on it.

Next is the spring guide. This also has absolutely no grease applied to it.

Finally, here is the entire receiver.

That covers most of the parts.

Next, let's consider the details of the customization.

Custom policy determination

To recap from last time, the request was as follows:

Based on the request, the following parts were gathered.

will be important.

For this project, I'll be using Bellhammer Gold No. 2 and low-viscosity No. 0 grease.

Now let's customize it.

Custom

First, we polish the area where the receiver's moving parts make contact.

This time, we'll be using a rotary tool to polish the surface.

It's incredibly easy. If you were sanding with sandpaper, you'd never have enough time.

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.

Here's the polished receiver. Let's also polish the feeding route area.

After polishing

You can see the difference in the photos.

All that's left is to assemble the non-binding springs and apply grease to each part.

Basically, for metal-to-metal sliding parts, we apply Bellhammer Gold No. 2, and for resin-to-resin or resin-to-metal sliding parts, we apply Bellhammer 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.

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'll apply Tokyo Marui high-viscosity grease to the spring just to be safe.

Tokyo Marui genuine high-viscosity special grease
This is a standard grease.

I assembled it like this for now, but the muzzle velocity with 0.2g BBs was only a maximum of 88m/s, which wasn't enough, so I'm going to make a spring heightening washer out of plastic sheet.

Measure the diameter of the spring guide.

I made three height-raising washers (3mm total) out of 1mm plastic sheet to raise the inner diameter. Incidentally, when assembling an uneven-pitch spring, the tightly wound side should face the spring guide.

Next, we'll customize the hop-up system.

First, here are the genuine parts.

Let's take a look at the barrel.

Here, we enlarge the hop-up hole and taper the barrel tip to make the hop-up more effective.

I'll grind it down with a rotary tool.

Here is the finished barrel.

There are burrs remaining in the hop-up holes, so I'll use a diamond file to smooth them out. Then I'll temporarily assemble the hop-up and check how the hop-up protrusions descend.

It's coming down nicely.

Now we'll assemble the remaining parts.

This is completed.

I forgot to take a picture, but the base of the inner barrel was wobbly, so I wrapped masking tape around the tip to stabilize it.

Live-fire performance verification

Now, as usual, let's check the actual firing performance.

The temperature was approximately 22℃, and the ammunition used was S&T's 0.2g bio BBs.

First, it's non-hop.

From here, apply hop-up until the initial velocity is at its maximum.

92 m/s is pretty good.

It doesn't quite reach my desired 95 m/s, but adding any more would make cocking heavier and negate the advantages of the CA870, so I'll stop here.

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

Next is sound.

First, here's a video of the firing sound without a silencer.

Maruzen CA870 Custom

This is a video of the sound of a gun firing with a silencer.

Maruzen CA870 Custom Silencer

I think it's become considerably quieter. It's hard to tell from the video, but with the silencer attached, the firing sound is almost completely eliminated, making it very quiet.

I don't think you'd be able to tell the difference from about 5 meters away. In fact, the cocking sound is louder.

The original sound was a springy, bouncy noise, but it's completely gone now.

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.

Completed state and summary

Finally, I'll try putting on some random accessories I have at home.

This is a site picture.

The silencer attaches flush with the outer barrel, which looks great.

Summary

In summary, the final specifications are as follows:

Angs Nonbyne Spring 0.9J
The spring noise disappears. I've personally used it a couple of times, but I don't think it alone will get you to 0.9J. If you're going to be shooting indoors, I recommend choosing 0.8J and keeping the initial velocity of a 0.2g BB under 90m/s.

KM Planning Maruzen Shotgun Series Compatible Silencer Adapter, 14mm Reverse Thread
As you can see in the operation video, it becomes even quieter when a suppressor is attached, so I recommend it. Plus, it has a 14mm reverse thread, so it can be used with most suppressors.

This only involves my labor and the custom-made spring heightening washers.

It's become quite quiet, making it a good airsoft gun for snipers who prefer to hide and fight.

I plan to hand it over to my friend during an airsoft game, so I'll check the trajectory there.

That concludes the explanation.

Finally, as is customary, here's a product introduction: the old HOP version is basically no longer in stock on the market, so if you're considering purchasing the Maruzen CA870 series, please refer to the review article for the new HOP version.