RetroArms CNC Steel Gear Set PandoRA 20:1 (4mm)

RetroArms PandoRA CNC steel gears with 4 mm shafts

This expert product description was prepared by the ANAREUS.cz expert team. All rights to this unique content are bound to the anareus.cz domain.RetroArms PandoRA are CNC-machined gears designed for AEG builds where mechanical durability of the gear train is the priority. Unlike gears assembled from several separate components, each PandoRA gear is completely CNC-machined from a single block of high-quality steel. The gears use reinforced 4 mm shafts, and the set includes a bevel gear, spur gear and sector gear. Before starting production, the manufacturer tested the gears in a RetroArms CNC gearbox with an M210 spring for 10,000 shots without signs of wear. Correct installation is essential: 4 mm shafts are not compatible with standard bearings designed for 3 mm shafts, so bearings with a 4 mm inner diameter and corresponding 4 mm shims must be used. During assembly, the gears must also be shimmed correctly, motor engagement must be adjusted and the AOE between the sector gear and piston must be checked.

Overview of RetroArms PandoRA gear ratios

* Note on DSG (Dual Sector Gear): Because the piston compresses the spring over only approximately half the travel compared with a standard sector gear, achieving a typical performance of around 120–130 m/s generally requires a stronger spring, typically M140 or higher. The resulting performance also depends on barrel length, cylinder volume, air seal, piston weight and the specific DSG configuration.

Technical specifications

• Series: PandoRA
• Type: CNC gear set for AEG
• Gear ratio: 20:1
• Material: Steel
• Manufacturing: CNC-machined from a single piece of material
• Shaft diameter: 4 mm
• Required bearing inner diameter: 4 mm
• Required shim inner diameter: 4 mm
• Manufacturer testing: 10,000 shots with an M210 spring in a RetroArms CNC gearbox

Package contents

• PandoRA 20:1 steel gear set (4 mm shafts)

Frequently asked questions (FAQ)

Can PandoRA gears with 4 mm shafts be used with standard AEG bearings?

No. Standard AEG gears commonly use 3 mm shafts, while this PandoRA version has 4 mm shafts. You therefore need bearings with a corresponding 4 mm inner diameter.

Do I also need special shims for installation?

Yes. Due to the 4 mm shafts, shims with a 4 mm inner diameter must be used. Standard shims designed for 3 mm shafts are not compatible.

What does the gear ratio mean?

The gear ratio determines how many times the motor must rotate for the gear train to complete one full gearbox cycle. In general, a lower ratio means a faster cycle, higher rate of fire and quicker trigger response, but it also places greater demands on the motor, battery and correct tuning of the entire build. This is why 10:1 and 13:1 ratios are typical for high-speed builds, 16:1 represents a versatile compromise between speed and load, while 20:1 provides greater mechanical advantage for stronger springs and high-load builds. A specific category is represented by DSG T8 and T9, where the sector gear engages the piston twice during a single revolution and uses only part of its stroke – the result can be an extremely high rate of fire, but such a build requires experienced tuning, a suitable motor, electronics, battery and usually a significantly stronger spring. The gear ratio itself therefore does not determine the gun's power; it primarily changes the cycle speed, motor load, current draw and overall characteristics of the AEG build.

What should be checked when installing PandoRA gears?

In addition to using the correct 4 mm bearings and shims, the gears must be shimmed correctly, motor engagement adjusted and AOE checked between the sector gear and piston. In high-performance builds, precise adjustment of the gear train has a major influence on correct operation and service life.