When I was customizing my PTS Masada, I couldn't find a commercially available hop-up packing and bucking that I liked.
I also own a Tanaka airsoft rifle, and since there are no aftermarket hop-up packing parts available, I had been planning to make one myself later, so I thought this was a good opportunity to try it.
Previously, I was using Tokyo Marui's genuine hop-up packing and PTS Masada's genuine hop-up rubber, which produced a decent trajectory, but I really wanted to implement a long-range hop-up, so I decided to create a hop-up packing based on the G-HOP.
Since I have the opportunity, I'd like to introduce the production process. I'd also like to compare the appearance of MAPLE LEAF and Miyagawa, which I often use.
First, let's look at the process of modifying the inner barrel.
*This article aims to provide educational explanations from a mechanical engineering perspective regarding the safe hobby use of airsoft guns.
This does not promote acts of violence, the use of weapons, weapon modification, practical evaluation, or violation of laws and regulations.
Processing of the hop-up window on the inner barrel
First, here is the hop-up window on the unprocessed barrel.
The area enclosed in the red square has a wall that rises sharply (less than 45 degrees) from the hop-up window to the outer circumference of the barrel. Use a rotary tool or file to smooth this out.
This is an example of the processing method. The goal is to erase the parts of the image that are filled in yellow, so that they look like red lines.
The purpose of this processing is to smooth out the deformation of the rubber when the protrusion of the hop packing descends, thereby improving the seal with the window, suppressing deformation of the protrusion, and allowing the protrusion to descend with less force.
Also, there are always burrs on the inside of the hop-up window. These burrs are unavoidable in mass production processes (adding manual processing to the process is too costly). Since it's impossible to remove the burrs with machines and can only be done by hand, both genuine and aftermarket parts basically have burrs, so you should lightly file them off with a round file.
Here are the finished products.
You can see that the corners of the hop window are rounded. Now, all you have to do is smooth it out with #1000 grit sandpaper and you're done.
Please wash it thoroughly.
I think this modification is effective for any hop-up packing, regardless of whether it's G-HOP or not.
The reason why this kind of processing is rarely done on genuine or aftermarket parts is simply because machining it would increase processing time and make it difficult to ensure precision, thus drastically increasing costs.
That's why even a major domestic manufacturer known for its high accuracy probably wouldn't do it. A very expensive aftermarket inner barrel might have a similar modification.
In some cases, this process might also involve extending the hop window.
I'll introduce the tools I use.
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.
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.
Tungsten bit for rotary tool, shank diameter 2.35mm
Tungsten, the second hardest material after diamond, is recommended considering the price. It cuts very effectively.
That completes the inner barrel assembly.
Let's try making a regular G-HOP.
I tried making a G-HOP using the method introduced by Gunzineer. I made it using scraps of genuine Tokyo Marui hop-up packing.
First, attach the hop packing to the hop window to increase its capacity.
Cut off the excess.
Then, a rubber sheet called a spin sheet is attached to the projectile to provide resistance.
All that's left is to put on the slick packing and you're done. By the way, I'm using Miyagawa's slick packing.
I wanted to show you the chamber I installed, but the results were so disappointing that I don't have any photos, so I'll explain it with a drawing.
Because I added extra spin sheet material and covered it with a slick packing (which increased the outer circumference of the hop-up packing), the fit with the chamber became too tight, and the spin sheet flexed and came out even without applying hop-up. It was quite a lot.
I tried cutting off the excess parts and making adjustments, but it didn't work. Since I couldn't adjust the hop at all, I gave up and thought about what to do next.
Looking back, the combination of Miyagawa-san's slick packing and the G-HOP system with the PTS Masada chamber might not be a good match.
Creating a modified G-HOP
I may have sounded grand by calling it a "G-HOP Kai" (modified G-HOP), but all I did was change the material of the spin sheet and remove the extra layer of material from the hop window.
I cut up a spare hop-up bucking from a Krytac Kriss Vector that was lying around (a thick, firm rubber is recommended). It was slightly firmer and thicker than the original Tokyo Marui bucking.
When you assemble the slick packing and put it into the chamber...
feel well.
Now, let's assemble the chamber with the hop-up rubber attached and check the hop settings at 0 and MAX. (Because it's a Masada model, the chamber is separate from the barrel and hop-up mechanism.)
The left image shows hop 0, and the right image shows hop MAX. Sorry for the different angles.
It looks good. However, with 0.2g BBs, the hop-up might be too strong even at hop-up 0, so adjust the amount of hop-up when hop-up is 0 by attaching a 0.1mm plastic plate as shown below.
This is completed.
By the way, I used a leftover flat hop rubber from Laylax, cut to the right length to fit the hop window, and attached it.
With this setup, the initial velocity is about 93 m/s with 0 hop-up and 0.2g BBs, and about 70 m/s with hop-up at maximum, so the hop-up is effective.
However, about one in ten shots will have a significantly different muzzle velocity, so there will probably be flyers.
For more details on this, please see the PTS Masada custom article.
Troubleshooting and Solutions
In early April 2021, when we attempted to conduct a ballistic comparison, we encountered a problem with the G-HOP system we had created.
For some reason, the night before I got drunk and, in an attempt to prevent frying, I disassembled the MASADA hop-up and stuck a 0.5mm plastic sheet onto the surface of the flat hop tensioner.
The goal was to increase the tension of the hop packing in order to reduce the amount of fryer in the modified G-HOP.
I was drunk, so I took it into the field without checking if it was working at home.
When I test-fired the gun at the field's range on the day of the airsoft game, the BBs jammed and wouldn't come out. The reason was that I had added a 0.5mm plastic plate to increase the hop-up, which made it stick out too much and prevented the BBs from coming out.
Since there was no other option, I tried rebuilding it using the hard tensioner (stiff) that came with the Laylax flat hop tensioner I was using, but it was a failure as the BBs wouldn't fire even at zero hop.
After much thought, I decided to use the long-range brook from Miyagawa's brook set that I already had on hand.
Also, it seemed like there was too much hop-up, so I added two 0.2mm plastic sheets to both ends of the hop-up window of the inner barrel to make it 0.4mm thick and attached them to increase the hop-up height.
With this setup, using 0.2g BBs with hop-up set to 0, the muzzle velocity was 93m/s, with an accuracy of ±0.3. The flyer effect also disappeared.
It's done.
G-HOP Modification Creation Procedure
The order in which to create the PTS masada for this project is as follows:
Here's a list of the necessary tools.
Miyagawa Rubber Hop Packing, Flat Type, 3-pack, Nitrile Rubber, Hardness 60
This is used as material for G-HOP. For 0.20g BBs, a hardness of 50 is recommended.
Miyagawa Rubber Push Rubber + DIY Kit
I'll use it as material for rubber buckings.
・Loctite instant adhesive with brush
The brush makes it incredibly easy to use.
Tamiya plastic sheet thickness0.2mm
It's incredibly convenient for small crafting and fabrication projects. The possibilities are endless.
Performance verification
We carefully assembled it and measured the muzzle velocity with a chronograph.
The ammunition used is Tokyo Marui 0.2g Bio BBs.
The initial velocity was 92 m/s, and even after applying hop-up, it barely dropped, only going down to a maximum of 89 m/s.
Moreover, the initial velocity fluctuation range was reduced to a mere ±0.2 m/s. That's the power of long-range firing!
If you're interested, please also check out my review of the chronograph.
Also, the flyers that were a concern have been removed.
Next, we'll check the ballistics.
Next time, we'll check the ballistics.
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