King Arms m4a1 spring
 

Hello all, I recently got a King Arms m4a1, and did a few improvements on it. My friends spare parts box contributed a lot to it, but it got a madbull tightbore barrel, a different piston head (no idea which one) and a ball bearing spring guide. We chrono'd the gun at about 370-380. I mostly play CQB though, so I need it under 350. It has the stock spring right now, and I don't know what the stock one is, so right now i'm trying to figure out which spring I should get to drop under 350 fps.

An M90.

I get an average of 330 in my KA with a m90

On my King Arms M4A1 I got 330fps with a SHS M90.

well that seems fairly definitive. I'll pick one up and try it out. Thanks! I will also try and get some photos up of this thing once I have everything all nice on it.

By the way... Anyone chronoed a totally stock Kingarms M4A1? I want to reuse the spring but not sure of its power.

Forgot to do that before diving into it. but with a tightbore (6.03mm) and a better piston head, and having it shoot 370-380. I would say it was likely around 350 stock perhaps?

My stock spring shot at 400 fps with .2s

400 with .2s? that seems rather fast, I was using .2s when i chrono'd too. I'm not sure how that makes sense.

Did you turn the hop-up to minimal when you chrono'd it?
Or check the air seal around the hop-up and the new barrel?

an m95 spring got me 350fps +/- 1-2 with this setup.