TM L96 AWS Spring options?

[Starkeyj]

Hello,

I have a TM L96 AWS upgraded with aspuk parts (Steel cylinder, cylinder head, piston, spring guide, M135 Spring, KM TN 6.03 TBB)

I used it today and it chronos at 440fps on .2g bb's.

I want it bang on 500fps but I can't find a suitable spring, I have heard I can cut down a VSR10 spring by about 4cm to fit, this would lower the fps output of the spring I believe?

Could someone recommend a spring which will bring it closer to the 500fps mark?

Thanks