RetroArms CNC V2.5 / SR-25 QSC Split Gearbox (8 mm)

RetroArms CNC split SR-25 QSC gearbox

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 SR-25 CNC gearbox is an extended version of the V2 design known as V2.5, intended for AEG airsoft rifles based on the SR-25 platform. Both halves are fully CNC-milled from a solid block of EN AW 7075 T651 aluminium alloy rather than cast, and fit together precisely, including coaxially aligned holes for 8 mm bearings. The redesigned generation features thinner outer walls for improved fit inside SR-25 receivers, a modified front section for compatibility with a wider selection of hop-up units and smaller cylinder head locating posts for improved compatibility with parts from different manufacturers. Servicing and tuning are made easier by inspection openings for AOE and piston position, gear lubrication holes and access for releasing the anti-reversal latch. The trigger contact area has also been modified, including the removal of problematic radii for the installation of ETU units, while the centre pin opening has been enlarged for improved fit in certain non-standard receivers. Wiring can be routed through an opening beneath the motor post, where it is protected by a machined tab. The design also uses new formed threads, high-strength socket head cap screws, additional machine-chamfered edges and air intake openings for the pneumatic system. Precision holes for the anti-reversal latch and trigger, together with micro-grooves on the spring posts, help keep small components in place while assembling the gearbox. The integrated QSC system enables quick spring changes, and the assembly includes the corresponding CNC spring guide. The manufacturer states that the gearbox has undergone long-term testing with an M160 spring. The gearbox can be used in most compatible SR-25 rifles, but due to differences in manufacturing tolerances, not every combination of receiver and internal components can be considered Plug & Play. The manufacturer does not recommend this version for Classic Army guns, and installation itself requires experience with building and tuning AEG gearboxes.

Key features

Technical specifications

• Type: Split CNC gearbox V2.5 / SR-25
• Material: EN AW 7075 T651 aluminium alloy
• Manufacturing: CNC milling from a solid block of material
• Bearing hole diameter: 8 mm
• Spring change system: QSC
• Spring guide: CNC, included
• Assembly screws: High-strength socket head cap screws
• Bearings: Not included
• Manufacturer testing: Long-term tested with an M160 spring
• Compatibility: Most SR-25-type AEG airsoft guns
• Compatibility limitation: Manufacturer does not recommend it for Classic Army guns

Package contents

• 1× RetroArms CNC split gearbox V2.5 / SR-25 (8 mm) QSC
• 1× CNC spring guide
• 2× M2.5 × 3 screw
• Assembly hardware
• 1× RetroArms sticker

Frequently asked questions (FAQ)

Is this gearbox the same as a standard V2 gearbox for an M4?

No. This is an extended V2.5 design intended for the SR-25 platform. Before purchasing, it is therefore necessary to verify that the specific gun uses the corresponding SR-25 gearbox type.

Does the gearbox fit every SR-25 airsoft rifle?

RetroArms has modified the design for compatibility with the vast majority of common SR-25 rifles, but different manufacturing tolerances between brands may require additional fitting. The manufacturer also does not recommend this version for Classic Army guns.

Are 8 mm bearings included?

No. The gearbox has holes for 8 mm bearings, but the bearings themselves are not included. They therefore need to be selected separately according to the planned build.

Is the RetroArms SR-25 CNC gearbox a Plug & Play part?

No. Although the design is engineered for broad compatibility, installation requires expert knowledge of AEG gearbox assembly. The gears, piston, pneumatic system, wiring, hop-up system and other components of the specific gun must be correctly fitted and tuned to work together.