Systema Non-Linear Irregular Pitch Airsoft AEG Upgrade Spring
(Power: M150)

"I bought the M 130, installed it in my Specna Arms SA-J09 and chrono'ed 470 fps. Spring is OP.

"Been buying Systema springs for at least a decade so I'll chime in: lot of springs out there on the market and I've tried almost all of them. At the end of the day I come back to Systema for quality and consistency of spring rate. Your results may vary depending on numerous factors, but once you've gained a certain degree of experience and worked out the kinks in your builds, it's nice to know you can depend on a certain spring rate to provide certain results...consistently. That's Systema.

"Used the M140 spring to upgrade my factory M120. Stock gun with 18:1 gears, 30k/21 TPA motor, 11.1 Li-ion Titan

Chrono STOCK:
BB RPS FPS
.2 22 395
.25 22 355
.28 22 335

Chrono M140:
.28 18 425

Seemed pointless to test the others. Good Spring.