We tested 150, 200, 230procent variation springs with most leading buckings.. But our 300procent gave 100procent feeding consistency in most SS (short stroke) applications.
The shortstroke segment, is made from a bouncy material, effectivley taking the impact of the bolt, and bouncing it back. Hence why we nickname this kit, the “Bouncer”.
This material property lessens the shock to the rear sight assembly.
As used by numerous YouTube airsofters across the globe. Install, and welcome to the BRRRTTT family.




