ZCI M110 Spring
A great spring for the money. With perfect compression my friend's M4 I built using this was chrono'ing a consistent ~375fps and stayed around that until settling to ~350fps where it's at now. Very consistent shot to shot and hasn't begun to bend, warp, or flake like other springs after ~10,000 rounds.
Date Added: 09/16/2016 by Jerichow