ACM M90 AEG Spring (SP90)

Bring your airsoft rifle under strict indoor velocity limits while boosting cycling performance with the ACM M90 AEG Spring (SP90)! Designed as a drop-in power tuning spring for Airsoft Electric Guns (AEGs), this lightweight main power spring allows players to quickly adjust their muzzle velocity to meet CQB arena rules without sacrificing trigger response or electrical efficiency.

High-Tensile Steel Construction & Non-Linear Winding Crafted from high-grade, heat-treated alloy spring steel, the ACM M90 spring is engineered to maintain consistent tension over thousands of firing cycles without shrinking or losing output power. It features a non-linear (variable pitch) coil configuration that spaces the spring coils unevenly along its length. This smart winding design lowers the initial torque required by your motor and gear set at the start of the piston pullback, dramatically reducing battery draw and mechanical startup resistance. Once pulled back, the spring releases clean, linear forward momentum to push the piston smoothly through the cylinder assembly.

CQB-Friendly Muzzle Velocity & Ultra-Fast Cycling In a standard AEG build featuring efficient air seal components (using 0.20g 6mm BBs), an M90 rating typically yields between 280 and 320 FPS. Because the lower spring tension places far less strain on your motor, gears, and piston teeth, your gearbox achieves significantly faster full-auto rates of fire (ROF) and snappier semi-automatic trigger response. Both ends of the spring are ground flat to sit completely flush against bearing spring guides and piston heads, preventing spring binding, twisting, and lateral wear inside the gearbox shell.

Universal AEG Gearbox Fitment Manufactured to standard airsoft main spring dimensions, the ACM M90 is universally compatible with Version 2 (M4/MP5/G3), Version 3 (AK/G36), Version 6 (P90), and quick-change spring gearbox platforms. Whether you are downgrading a high-FPS outdoor rifle for indoor play, tuning a high-speed CQB build, or extending the lifespan of stock internal gearbox components, the ACM M90 AEG Spring (SP90) delivers exceptional value, smooth operation, and long-lasting durability.