Prophet's GBB tech thread.

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TheProphet
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Prophet's GBB tech thread.

Postby TheProphet » Tue Jan 07, 2014 2:24 pm

Well, this is my first write up of a build so please bear with me. Feel free to leave any comments or questions you may have of course.

I was contacted by a member on Airsoft Society wanting me to fix and upgrade their WE 3.8 hicapa. Upon receipt I test fired everything. On test fire, the slide would not blow back all the way, instead getting caught halfway back instead of finishing the cycle. I also found that the gun must be cocked in a certain way otherwise it would catch and be hard to cock. I deduced, after feeling some grinding when cocking the gun, that the blowback unit (BBU), was sitting too low. Pretty easy fix. I informed the owner of the gun what the problem was and he ordered the following parts:

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Upon receipt of the parts the first thing I went for was the high flow valve, the easiest part to install. Or so I thought. Turns out, as you can see in the following picture, the new valve (right) is much shorter than the original (left):

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Because of this, the valve knocker was unable to reach the valve and would not release gas, so the part was scrapped from the upgrade list after consulting the owner.

The next part I decided to install was the spring set. Given that stock springs in a 3.8 hicapa are around the 120% area and the upgrade springs chosen by the owner were 170%, I was a little leery of this. As you can see from the pictures below, the upgrade springs (right) are far longer than the stock springs (left):

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Due to this, and the gun being smaller than the standard 5.1 that the springs are designed for, the springs required modification to work correctly. In order for the hammer spring housing to fit back onto the grip, I used my dremel to remove 3 coils from the spring.

The recoil spring was also much longer than the gun could handle. In the original form, the slide would not have enough room to completely compress the spring when blowing back, resulting in no feeding. In order to fix that, I removed a total of 5 coils, again using my dremel, from the spring. Taking it from this:

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To this:

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(both pictures taken next to the stock spring)

Next to install was the new bucking/inner barrel. This install was extremely straightforward and probably the simplest part of the job. Or so I thought. Thanks to WE's poor quality, one of the main posts of the hop up chamber broke off on reassembly, as you can see here:

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Luckily, I had a spare hop up chamber and was able to swap the parts easily.
Stock barrel/hop:

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New barrel/hop:

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Next project was replacing the stock nozzle (left) with the new Angel Customs nozzle (right). This was a challenge as the internals of the nozzle had to be transferred over, using the tiny little screw you can see on the new one. Exceedingly frustrating to work with.

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Next was the blowback housing and the piston head. You can see the stock housing on the left and the Angel Customs housing on the right.

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The Angel Customs used a different piston style than the stock housing, so the piston head was set aside at first:

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Come to find out, the AC housing did not properly fit the hicapa slide and was therefore put aside. This mean that we could now replace the stock piston head (first picture) with the new piston head (second picture, seen assembled on the piston).

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Once the new piston was assembled, all that was left was final assembly. Unfortunately the nozzle return spring had become warped during the trial and error process with the AC housing. After contacting the owner, he sent a new one and I was able to complete the assembly. You can see the new spring (left) next to the warped spring (right):

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Here you can see the blow back unit completely assembled:

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During reassembly I noticed the stock slide catch was worn down and would no longer stay in place, so it was replaced with a spare slide catch I had laying around, an extended version. Once I got the gun completely assembled everything worked smoothly. Due to the increased recoil spring vs the short slide the gun had a quick return time on the slide, allowing for faster follow up shots. The trade off, however, was incredibly reduced gas efficiency. I then tuned the hop up for .28s (weight the owner requested it be tuned to) and chrono’d the pistol. In 50ish degree weather with propane the pistol fired a max of 300 FPS with a .20 BB and a low of 279 at the same weight.

Finished product:

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Even with all of the issues with fitment and such, I quite enjoyed doing this build. I hope you enjoyed reading about it.
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Airsoft Gi Darren
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Re: Prophet's GBB tech thread.

Postby Airsoft Gi Darren » Wed Jan 08, 2014 10:18 am

Nice write up!
TheProphet
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Posts: 54
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Re: Prophet's GBB tech thread.

Postby TheProphet » Wed Jan 08, 2014 1:30 pm

Thank ya. I'll be documenting all of my teching ventures here, including a guide on how to reseal your mags and fix leaks.

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