400 FPS with M100 Spring????

[tybo935]

My goal is to shoot 350 FPS for CQB so I installed a used M100 Spring in my gun and now it is shooting 400 FPS??? Is it because I have good air seal because even with a good air seal that seems almost impossible. What are the chances it was miss-marked by the company (SHS). Yes I broke in the spring. Its frustrating to me because if I want any lower spring I may have to get a swiss cheese light weight piston.

[T6e9a]

The chances of SHS springs being mislabeled is quite high. Known by the teching community as taking a gamble with the ACM(all china made) lottery.
And even if it is properly labeled, along with the compression components, other factors play into FPS moreso than piston weight. Cylinder volume and barrel length/bore have a much bigger role than piston weight.

I would suggest cutting a couple coils off the spring if you aren't able to get your hands on an M90 spring. Start with 3, and go from there.

Alternatively, depending on your gun/cylinder volume/barrel length, you could also short stroke the sector gear, which effectively doesn't pull the piston back as far per cycle. General rule of thumb for short stroking (or SSing) is about 15fps/tooth. That is only a general guideline, not solid fact for every build. I usually start with 2 teeth if im trying to go for 350 from 400. But again, short stroking is more ideal for medium-shorter barreled replicas that don't require a full cylinders volume for ideal function.