TM GBB Pistol Upgrade Stages

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TM GBB Pistol Upgrade Stages


Stage 1

For the Tokyo Marui GBB pistol, the most basic and economic upgrade for the gas blowback pistol are as follows.


  • Change the front sight to a Fiber Illuminated Sight, to ease target acquisition.
  • Short stroke the recoil spring to significantly increase the cycle speed and gas efficiency (Note, however, that this action will disable the slide catch).
  • Install an aftermarket magwell - this will allow smoother and easier reloading. If you are using the pistol for competition, then you can choose a more flamboyant color for a race gun style; if the pistol is to be used for gaming, a lower profile dark color is a much better choice.


Given these build conditions, and depending on how good the maintenance is and how much the shooter fires the pistol, the weapon will last for several months to a year. Following this, cracks may appear on stock plastic nozzles and/or slides; this is normal, however, as stock TM slides and nozzles were designed for use with lower pressure Duster Gas. Once this occurs, the pistol can be repaired with stock replacement parts, or it can be upgraded to the Stage 2 level.



Stage 2

The second stage of the upgrade process focuses on moving to a metal slide to circumvent the cracking issues found in the Stage 1 stock plastic slides.

Most commonly used are aluminum slides, preferred for their low mass and high strength. These properties result in high gas efficiency and crisper recoil when compared to a slide of comparable build made of a different material, such as Steel.

Additionally, budget allowing, a change to an aluminum outer barrel and aluminum blow back housing is also recommended, to balance the slide’s weight for better cycling. That said, however, an aluminum slide and stock TM housing will still adequately improve cycling smoothness, albeit with increased recoil and reduced gas efficiency due to the higher mass.

For competition shooting, gas efficiency, cycling speed, and stability are characteristics more sought after than heavy recoil.


Last but not least, reinforcing or buying an improved hammer and recoil spring will serve well to improve reliability and smooth out cycling. These springs are often sold by percentages: 100%, 130%, 150%, 200%, and so on. These percentages represent the amount by which the spring is stronger than a stock spring. In other words, a 150% spring will be 1.5 times stiffer than a stock spring for a comparable pistol. Note that using these springs will result in different properties in shooting and handling, however. A stronger recoil spring will result in less felt recoil but increased cycle speed. A stronger hammer spring will result in more gas flow per cycle. These must be properly controlled and balanced in order to achieve optimum results.



Stage 3

Stage 3 is the last upgrade stage, which focuses on better airseal, and a more responsive trigger. Note that many players choose to put in Stage 3 upgrades before Stage 2 ones; this is entirely up to choice, and it is up to the player to see which set of upgrades (and subsequent performance properties) they prefer.

To improve compression, all the parts that handle the gas flow must be upgraded. Although the nozzle is not an essential upgrade, it can be considered. The piston head should also be upgraded, replacing the piston cup that many stock pistols have. Following this, the Inner Barrel and Hopup bucking should be upgraded. Recommended upgrades to these include PDI 6.01mm barrels and Nine Ball 6.00mm barrels, as well as PDI W Hold or Nine Ball Hopup buckings. If desired, and budget allowing, a new Hopup Chamber (For example, the UAC Hopup Chamber) will further aid in improving airseal.


To improve the trigger assembly, parts that provide a crisper, cleaner feel to the trigger are desired. A ‘crisp’ trigger is one that has minimal slop, or movement before the break of the hammer; a clean break, or point of hammer release; and a solid and noticeable reset. Parts for each pistol vary, and research should thus be done in order to find the trigger parts that best fit each individual user.


Upgrading the hammer assembly can also improve trigger response and tactile feedback. An aftermarket hammer or hammer assembly (or modifications to the stock hammer) can result in great improvements on trigger response and hammer response. Stock hammer modification requires more time and is hard to get it done right. It requires certain skills, the concept is not difficult to understand. To accompany these upgrades, an improved hammer spring can also be installed, as mentioned above. Note that for hammerless or striker-fired pistols such as the Glock, M&P, FNX, etc. the model will still have a hammer; it will simply be internally contained. Thus, the hammer upgrades can still be done to hammerless pistols.




After all the above upgrades have been completed, the only thing left to guarantee long-lasting performance will be maintenance. If any stock parts are broken, simply replace them with reinforced steel parts and they should offer a significant extension to the pistol’s lifetime.

Cleaning & Lubrication

Note, however, that extensive upgrades are not required to make a TM Pistol gameable, or even reliable. Left totally stock, most TM Pistols will outrange, outshoot, and outlast other weapons on the field. It is an entirely capable platform without modification, and thus these upgrades should be seen as voluntary in the search for improved performance, rather than necessary to bring the pistol to a gameable standard.


1 comment

  • Posted on by Eddie Green

    This comment is more directed to your aeg guide.
    Spectacular explanation! Im a member of a well known airsoft forum. I find myself arguing with people who self proclaim themselves as airsoft experts all the time about some of the very things you mention. Your process is the same as mine except for barrel and mosfet choice. I subscribe to the school of thought that extreme tight bore is not a good choice due to bb tolerances. I will install nothing less and nothing more than 6.03. I dont see where anything tighter will attain goals reliably. As for mosfets, i have installed both btc and gates. I find the ability to install gates with the exception of the spectre (if you can get one) are much easier. The chimeras are a serious pia to install and come with crappy wiring. Im also not wild about the fact that btc uses mechanical switches.
    I simply wanted to thank you for stating all the points exactly as i would state them to remove the mystery from upgrading.

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