Custom Block IV – Gear Ratio

We don't optimise a single component. We optimise the entire system.

Custom Block IV – Gear Ratio is the fourth level of the PRIMOREGGIMENTO.COM upgrade programme, focused on refining the mechanical transmission of AEG airsoft replicas and achieving the best possible balance between the motor, gears, pneumatic system and electronics.

Starting from €299.00.

After improving accuracy, hop-up control, mechanical stability and pneumatic efficiency through the first three Custom Block levels, this service focuses on the drivetrain, which converts the motor's rotation into the mechanical cycle required to operate the replica.

The objective is not simply to increase operating speed, but to achieve a more responsive, smoother and more efficient mechanism, reducing unnecessary friction and mechanical stress without compromising reliability and long-term durability.

Each upgrade is carried out individually on the customer's airsoft replica, selecting the most suitable gear ratio and checking compatibility, tolerances, component fit and the characteristics of the existing motor and electronics.

Features and technical specifications

• Service: mechanical drivetrain and gear ratio optimisation
• Workshop: PRIMOREGGIMENTO.COM
• All work included in Custom Block III – Air Efficiency, including levels I – Precision and II – Hop Control
• Installation of a high-performance gear set with an optimised transmission ratio
• Installation of high-precision steel bushings where required by the configuration
• Complete drivetrain shimming
• Optimisation of mechanical friction and smoothness
• Inspection of motor-to-gear engagement
• Motor pinion height adjustment
• Complete mechanical lubrication
• Chronograph testing
• Final functional testing
• Components: high-performance gears, commonly including 13:1 ratios, and CNC-machined bushings where appropriate, selected according to the replica's platform and configuration
• Motor: any replacement is assessed separately and is not automatically included in the service

The drivetrain makes the difference

Every AEG replica has its own balance between motor performance, gear ratio, pneumatic load and electronic control system.

The motor generates the movement required for the firing cycle, while the gear ratio determines how rotational speed and torque are transferred through the mechanism.

Simply installing a faster gear set does not automatically guarantee better performance. A ratio that is unsuitable for the motor or configuration can increase mechanical stress, reduce operating consistency and compromise reliability.

Custom Block IV addresses the complete gearbox drivetrain, considering not only the gear ratio but also gear engagement, shimming, lubrication and correct interaction with the motor.

The aim is to achieve a transmission that works harmoniously with the rest of the replica, delivering a quicker response and a smooth, controlled mechanical cycle.

Why change the gear ratio?

The transmission ratio influences how quickly the motor completes the mechanical cycle and the load it must handle.

A lower gear ratio, such as the 13:1 configuration commonly used in high-performance builds, can improve response speed but requires careful assessment of the motor, mechanical components and electronics.

There is no single ideal ratio for every replica.

For this reason, we select gears according to the complete configuration, prioritising the balance between responsiveness, smooth operation, reliability and long-term durability.

The value of the service is not in installing the numerically lowest ratio, but in identifying the one that actually suits the replica.

Targeted improvements

• Improved trigger response
• Smoother and more consistent mechanical cycling
• Better balance between motor and drivetrain
• Reduced internal friction and unnecessary mechanical stress
• Better use of the installed motor's characteristics
• Improved mechanical reliability through proper component adjustment
• An optimised platform for potential future motor or electronic upgrades

Actual performance depends on the platform, motor characteristics, original configuration, manufacturing tolerances and overall condition of the replica.

Frequently asked questions

Does Custom Block IV include all previous levels?

Yes. Custom Block IV includes all the work covered by Custom Block III – Air Efficiency, which in turn includes Custom Block II – Hop Control and Custom Block I – Precision.

The fourth level completes the Custom Block programme by also addressing the transmission ratio, gear set and optimisation of the gearbox drivetrain.

Are 13:1 gears always installed?

No. A 13:1 ratio is one of the configurations commonly used, but it is not mandatory.

The selection depends on the motor, mechanical load, pneumatic system configuration and the replica's electronics.

Our objective is to identify the most balanced ratio for the system rather than installing the same gears indiscriminately across different platforms.

Will Custom Block IV necessarily increase the rate of fire?

Not necessarily.

A different gear ratio can influence the rate of fire, but the result also depends on the motor, battery, electronics and mechanical configuration.

The priority of Custom Block IV is to improve responsiveness and cycling consistency, rather than automatically pursuing the highest possible rate of fire.

Why isn't installing faster gears enough?

Because the gears must operate correctly with the motor and all the other components in the drivetrain.

A ratio selected without considering the complete system can cause excessive loads, friction, noise or inefficient operation.

Gear ratio selection, correct shimming and proper engagement with the motor pinion are therefore essential parts of the service.

Why are the bushings inspected as well?

Bushings support the gear shafts and help maintain their correct positioning during operation.

Their dimensional accuracy and proper fit within the gearbox affect drivetrain stability.

Where required by the configuration, the service includes the installation of high-precision steel bushings selected to provide suitable gear support.

Why is motor pinion height adjustment important?

The motor pinion must engage correctly with the drivetrain's bevel gear.

Incorrect adjustment can cause noise, friction and abnormal tooth wear.

During the upgrade, we check this engagement and adjust the motor position to achieve the smoothest possible operation.

Is the motor replaced?

Not automatically.

Many modern airsoft replicas already feature motors that are suitable for the intended configuration. Replacing them without a genuine technical need would add an expense that may not be justified.

We therefore assess the existing motor and consider any replacement separately, according to the replica's characteristics and the desired outcome.

Does the service include an electronics upgrade?

No, not automatically.

Custom Block IV optimises the mechanical drivetrain while taking the existing electronics into account. Any electronic modifications or upgrades are assessed separately.

A properly configured transmission also provides a solid foundation for future control system upgrades.

Will every replica achieve identical results?

No. Final performance depends on the platform, manufacturing tolerances, installed motor, electronics and component condition.

Each Custom Block is tailored to the individual replica rather than promising identical trigger response or rate-of-fire figures.

How is the work tested?

Every upgrade is completed with chronograph checks and functional testing to assess the replica's operation after gear installation and drivetrain adjustment.

The Custom Block philosophy

We have been studying, upgrading and refining airsoft replicas since 1997. In 2004, with the establishment of PRIMOREGGIMENTO.COM, this experience became part of our workshop's everyday work.

The Custom Block method has been developed through experience with thousands of replicas and continuous comparison of components, configurations and technical solutions.

Every replica has its own characteristics. The motor, electronics, drivetrain and pneumatic assembly must be considered parts of a single system rather than independent components.

The value of a Custom Block lies not only in the parts installed, but in the expertise required to select, adapt and adjust them to achieve the best possible balance between performance, reliability and long-term durability.

This approach is what distinguishes a straightforward upgrade from a PRIMOREGGIMENTO.COM Custom Block.