Split gearbox Version II (CNC, with Hop-up chamber, 9mm bearings) - RetroArms

Split Gearbox Version II (CNC, with integrated Hop-Up chamber, 9mm bearings) – RetroArms is a high-end solution designed for advanced airsoft builds and precise tuning of AR15 (M4) and M16 platforms. The gearbox shell is fully CNC-machined from a single block of EN AW 7075 T651 aircraft-grade aluminum with tensile strength up to 590 MPa, providing exceptional durability compared to standard zinc alloy gearboxes. The split construction consists of an upper shell, lower shell, and an integrated Hop-Up chamber that is rigidly fixed to the gearbox, ensuring perfect alignment between the gearbox and barrel. This design prevents Hop-Up movement during firing, improves shot consistency, and helps compensate for slight receiver misalignment in AR15 platforms.

The integrated Hop-Up chamber features a click-adjustable rotary system to prevent setting drift and a collet nut that securely clamps the inner barrel to eliminate movement. A QSC quick spring change system allows fast power adjustments without full disassembly. Numerous design improvements increase reliability, including reinforced stress points near the cylinder head, formed threads with higher strength, precision bearing seats to prevent rotation, enlarged wiring channels, and assembly-friendly spring retention features. An anodized surface finish protects the aluminum from corrosion. The gearbox is Tokyo Marui compatible and supports standard trigger contacts as well as popular electronic control units such as Gate.

Features:

• CNC split Version II gearbox for AR15/M4 and M16
• EN AW 7075 T651 aircraft-grade aluminum construction
• integrated Hop-Up chamber with click-adjust rotary system
• collet nut system for secure inner barrel fixation
• perfect gearbox and Hop-Up alignment
• 9 mm bearing support
• QSC quick spring change system
• reinforced critical stress areas
• formed threads for increased durability
• precision CNC machining and shell alignment
• Tokyo Marui compatibility
• supports standard trigger contacts and electronic control units
• anodized protective surface finish
• recommended nozzle length 21.3 mm