CNC split gearbox SR25 (8mm), QSC

CNC split gearbox designed for airsoft replicas SR25. This gearbox is manufactured from one solid block of aircraft aluminum (Dural) EN AW 7075 T651, which has higher strength (590MPa), than common construction steel (390MPa). Because of used material, our gearboxes have the best durability and resilience than common zinc-aluminum gearboxes. The gearbox is manufactured on precision CNC milling machines, directly in the RetroArms factory. Detail in bracket (8mm) means diameter for bushings/bearings.

Split gearbox means, that this gearbox is designed as a two part - Upper and Lower. Having a split gearbox has many advantages. For example much more easy installation of the inner parts into the gearbox. During setups of you cylinder set, there is no need of removing whole gearbox from your receiver, only upper part can be dismounted, because it‘s mounted on one receiver pin. This gearbox can be installed even into the receivers AR15 (M4), what are not completely straight, with any AR15 (M4) Hop Up chamber of your choice.

Package includes: CNC Split Gearbox SR25 (8mm) – QSC, set of screws and QSC spring guide.

RetroArms CNC gearboxes SR25 improvements:

• Spring holders have grooves, so the springs for tapped plate and trigger switch will not jump off.
• Sockets for bushings/bearings have smaller diameter about -0,02mm (7,98mm), for non-overturning the bushings during installation. The socket edges are cutted down for better installation.
• Enhanced grooves for wiring for 1mm, you can now use wirings with 2,5mm diameter.
• Added protecting edge for wiring against the motor.
• All threads are now shaped instead of cutted for better strength.
• Both of the gearbox parts are centered by milled grooves and edges.
• Added hole for releasing anti-reverse latch.
• For better durability, more material added around cylinder head part of the gearbox, this was the most critical part and 100% more material added where is huge radius.
• Added groove for anti-reversal latch spring, so it will not jump off.
• Outer edges are now cutted off.
• You can find what type of sockets gearbox have on the outside part of the gearbox (8mm or 9mm).

RetroArms gearbox has quick spring change system QSC, where you can put out whole spring guide with hex key and change the spring without need of opening the gearbox. In this solution, you need to secure spring guide with screw. Commonly with AR 15 (M4) replicas, it is by stock screw. In situations where you have folding stocks or no stock at all, you have to secure the spring guide with QSC screw. Otherwise there could be situation, where the spring guide will stuck with the spring. This is because the spring guide is not fixed in the gearbox but has will for easy removing with hex key.

Space for trigger switch is designed for compatibility with trigger switches, trigger units from common manufacturers for example: Gate, etc.

CNC gearbox SR25 has protective anodizing, even when it is problematic to anodize aluminum EN AW 7075 T651 (Dural), because of its high strength and hardness. If this material were not anodized, there would be huge risk of corrosion (huge gray spots with rotten look).

CNC gearbox can be installed only in airsoft replicas with Tokyo Marui compatible standard. That means even the inner parts. Do not use rude force during installation. Use only 1Nm tightening moment on screws, otherwise the screws will overturn in heads. There is no need of tightening screws with rude force, if you want to be sure that screws will sit perfectly, use thread glue or thread color.

You can use in CNC gearbox any spring of your choice, but be aware that stronger springs will result in lower durability.

!! Do not use MAXX cylinder head !!

Installation of the inner parts and gearbox requires professional knowledge, experience and skills. There are a lot of airsoft manufacturers on the market and every one of them create their own sizes, there are no standards like engineering ISO in airsoft. This is the main problem with a lot of inner and outer parts from different manufacturers which can be same product, but with different dimensions. We recommend using only parts from manufacturers with Tokyo Marui compatible parts, where should not be a problem with compatibility with CNC gearbox.