RetroArms SR25 Spring SiCr with Progressive Winding — M140 Trigger Guards this blowback unit offers unmatched

this blowback unit offers unmatched durability and reduced weight

EXPERT edition – full feature set unlocked

Manufactured from Silicon-Chromium (SiCr) spring steel

the M4P PRO model features advanced adjustment systems and locking mechanisms to ensure consistent tuning

Developed in collaboration with SpeedQB

RetroArms SR25 Spring SiCr with Progressive Winding — M140 Trigger Guards this blowback unit offers unmatchedThe RetroArms SR25 Spring SiCr with Progressive Winding M140 is a high performance main spring designed for SR25 and extended gearbox builds that require powerful and consistent compression. Manufactured from silicon chromium (SiCr) alloy steel, this spring offers superior resilience, reduced fatigue, and long term stability compared to standard carbon steel springs. The progressive winding design ensures smoother compression, reducing stress on the