How to build a Kublai based P1 Gel Blaster from scratch?

What is a GBB gel blaster? The acronym “GBB” stands for Gas Blowback that describes the blowback action of the gel blaster’s slide with the help of pressurized gas stored within the magazine. And the residue gas will be utilized to propel the gel out from the inner barrel. It is a very popular system due to the realism and experience it can offer to the user. 

GBB  requires gas to operate. The type of gas for a gel GBB blaster uses are the following; R134A gas, R220 gas, R290 gas, CO2, etc.

It is usually always recommended to use only the R134A gas if you have a stock GBB gel blaster that uses nylon slides. High pressure gas such as the Green Gas or CO2 will wear out the slide prematurely if not outright damage it catastrophically. Contrary to the popular beliefs that a high pressure gas can destroy a gel before it exits the inner barrel, it almost always is not due to the gas pressure but other factors such as the chambering process of the gel from the magazine lip into the inner barrel, inner barrel quality or even the size of the gel pellet itself. 

The magazine which stores the gas is the fuel for the entire operation of a GBB Gel blaster, without it it’s just a piece of plastic and some metal parts that won’t shoot anything but certainly a nice paper weight display piece nonetheless.  The Magazine is also one of the more expensive and delicate parts because if it does not behave like it should, your GBB gel blaster will not function properly. Thankfully the Magazine is a very serviceable part and it can be fixed with the O-ring seals or valve replacements made for it.

This blogpost will break it down for you to understand a Kublai based P1 GBB Gel blaster more parts by parts.

A GBB blaster typically consists of 2 major sections: Lower frame and Upper frame. 

Starting from the Lower frame it consists of the following parts: 

Frame, Chassis, Mag catch, Hammer assembly, Slide catch, Trigger and trigger bar.


Description of part


This is essentially the body of the blaster that houses all the components.


This part holds your slide and lower frame and trigger, etc together 

Mag catch

To eject or catch and secure your magazine in the frame. 

Hammer assembly

The hammer assembly is a critical component of the P1 Gel blaster. It primarily works with the slide to actuate the system by striking the magazine’s outlet valve.

Hammer assembly is made up with a few parts.

  1. Hammer Housing

  2. Hammer with Bearing

  3. Hammer Spring

  4. Sear

  5. Sear Spring

  6. Valve Knocker

  7. Valve Reset

  8. Valve Reset Spring

P1 Upgrade Spring and Pin Set

Core components for completing a build particularly if you build from scratch.

These upgraded springs are firmer than the stock one found in the stock Kublai P1.

Slide catch

The slide catch works in conjunction with the magazine's follower to catch the slide in the lock position when the magazine is out of gel.

Trigger and trigger bar

The trigger consists of  2 parts, the trigger itself and a trigger bar. When the trigger is pulled, the Trigger bar will push the Sear and actuate the hammer to start the operation.

Here are the parts for the Upper frame section: 

Slide, Housing, Chamber, Inner barrel, Sights, Outer barrel and Rear cover.


Description of part


The slide is the part where it houses the major components such as the outer/inner barrel and Blowback Housing, loading nozzle etc.

The slide comes in a variety of designs to suit your preference. Some come pre-installed with sights or have a different design/pattern for the slide etc.

BlowBack Housing

The Blowback Housing is one of the main components where the blowback action happens. It is typically made of metal, has a piston seal for the loading nozzle to create the blowback action.

In the case of Kublai P1, it comes in a set along with the Loading Nozzle and Loading Nozzle Return spring.

The Loading nozzle is the part that directs the gas pressure to actualize the blowback and also to propel the gel. This is done by a “rocket valve” housed within the loading nozzle. The loading nozzle also has the important task of loading the gel from the magazine into the chamber.

Chamber and inner barrel

This component can be further broken down into several parts.

The Chamber unit itself, typically made of metal, houses the Rubber bucking and keeps the inner barrel in place. It also has the important task of keeping the slide in place when it’s mated to the lower.

The rubber bucking is where the gel is seated and keeps the inner barrel in place.

Inner barrel is where the gel will be propelled through and shoot out the gel. Inner barrel upgrades typically are made of aluminum and built-in hop-up unit for better gel travel distance potential.

Recoil spring

This recoil spring rod keeps the slide in the battery position. Whenever the trigger is pulled and the slide is blown back, it will spring back to the battery position.

Iron Sight

Iron sight. Self-explanatory. It also does one very important job that is securing the blowback housing to the slide.

Plenty of iron sights styles available, regular iron sights, glow in the dark, raised height etc. Check for compatibility before purchasing.

Outer barrel

The outer barrel houses the chamber and inner barrel. Plenty of choices available.

Certain outer barrel has a 14mm CCW thread that you can install a suppressor onto.

Rear cover

To cover the back of the slide of the blaster.
Not every blowback housing has a separate rear cover. For example the Kubai P1 blowback housing has a fixed Rear Cover; The Kublai P1-S blowback housing has a separate rear cover.

Check and make sure before making any purchase.

There are also additional parts that won’t affect the GBB blaster itself as much for performance but more for quality of life changes. Example a Magwell Flare, what this does is when installed on the magwell of the lower, it enlarges the magwell and creates a slope inwards to the entrance making it easier to reload without looking at the blaster.

For a quick rundown for parts to make a Kublai P1 here is the list the bang for your buck (in Malaysian Ringgit).

Cheapest part for build a working Kublai P1:

Lower frame 

Kublai P1 colored frame 

Kublai P1 Chassis 

Kublai P1 stock nylon mag catch 

Kublai P1 stock hammer assembly 

Kublai P1 slide catch 

Kublai P1 stock nylon trigger with trigger bar 

Kublai P1 Magazine 

P1 Upgrade Spring and Pin Set

Upper frame 

Kublai P1 Stock Slide Assembly 

For tools you would need are the following:

  1. Phillips head screwdrivers 

  2. Tweezers

  3. Mallet 

There also special tools for GBB blaster that’s optional to have but you would an easier time doing maintenance for your blaster:

  1. Magazine valve tool

  2. P1 Workstation (is a magnetic workstation)

Valve tool is a tool for you to adjust the valve outlet of your magazine for the gas to flow.