RetroArms CNC Steel Gears Set PandoRA SR-25 20:1 (3mm)

RetroArms PandoRA SR-25 CNC Steel Gears With 3mm Axles

This expert product description was prepared by the ANAREUS.cz expert team. All rights to this unique content are tied to the anareus.cz domain.RetroArms PandoRA SR-25 are CNC-machined gears designed for AEG builds with an extended 19-tooth piston, where mechanical durability of the gear train is a priority. The gears are designed for extended V2.5-type gearboxes used in SR-25 rifles, as well as the PSG-1 gearbox (V4) and L85. Unlike gears assembled from several separate parts, each PandoRA gear is completely CNC-machined from a single block of high-quality steel. The gears use standard 3mm axles and the set includes a bevel gear, spur gear and sector gear. Before production began, 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; the 3mm axles are compatible with standard bushings or bearings for 3mm axles and corresponding shims. During assembly, the gears must also be properly shimmed, motor engagement adjusted and the AOE between the sector gear and piston checked.

RetroArms PandoRA Gear Ratio Overview

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

Technical Specifications

• Series: PandoRA
• Type: CNC gear set for AEG
• Gear Ratio: SR-25 20:1
• Material: Steel
• Suitable Piston: 19-tooth (SR-25 / PSG-1 / L85)
• Manufacturing: CNC machining from a single piece of material
• Axle Diameter: 3 mm
• Required Bushing / Bearing Inner Diameter: 3 mm
• Required Shim Inner Diameter: 3 mm
• Manufacturer Testing: 10,000 shots with an M210 spring in a RetroArms CNC gearbox

Package Contents

• PandoRA SR-25 20:1 steel gear set (3mm axles)

Frequently Asked Questions (FAQ)

What Does the Gear Ratio Mean?

The gear ratio determines how many motor rotations are required for the gear train to complete one full gearbox cycle. In general, a lower ratio means a faster cycle, higher RoF 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 are typical for speed-oriented builds, 16:1 represents a versatile balance between speed and load, while 20:1 provides greater mechanical advantage for stronger springs and torque-oriented builds. A specific category is DSG T8 and T9, where the sector gear engages the piston twice per revolution and uses only part of its stroke – this can result in an extremely high RoF, 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 gun power; it primarily changes the cycle speed, motor load, current draw and overall character of the AEG build.

What Should Be Checked When Installing PandoRA Gears?

In addition to using the correct 3mm bushings or bearings and shims, the gears must be properly shimmed, 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 impact on correct operation and service life.

Can I Use These Gears in an M4 or AK?

No. The gears are intended only for extended V2.5-type gearboxes used in SR-25 rifles, the PSG-1 gearbox known as V4, the L85 and the rare Classic Army MK17 (SCAR-H) version that uses a 19-tooth piston.