I purchased this spring to tune in my ICS M4 and keep it below our 400fps limit in Ohio. I am using a somewhat modified upper gearbox, with a G&G V2 ball bearing Metal Spring Guide I purchased here at ASGI, as well as a Modify Piston head and Systema Standard Black Piston and I am also using the stock cylinder and cylinder head. The spring now chronos at 384fps and an increase to 15.0bps, exceeding my goal and I am very satified with this Madbull product. I recommend the spring for anyone that wants a good solid FPS that for safety reasons will not hurt as much, but will definitely let the other team know they are hit. I also saw a 2.5bps increase over the 110 and 120 springs, which is a nice plus.
Great spring...very consistent FPS
Low variation in FPS, chronoed from 380.3 to 386.2 in 50 samples using a Madbull Chrono purchased at ASGI
Blue color easily identifies the spring from my others
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