SHS M110 Spring

This is an excellent quality spring, however it should be noted that in my M4 builds (with high quality parts throughout, sorboed, AOE corrected and good air seal) this spring consistently provides an FPS of about 365 with .25g BBs and a 370mm barrel with a slight amount of hop, and settles to about 350 within a few months. As a result, I use this spring regularly for standard field rifles. Not sure about the stated 390fps, but of course the platforms vary.