Hi all   I picked up my ICS m16 in 2006 and from the box it fired around 290 fps No idea what spring it has?.   Long story short I used it for a couple of weeks when i got it and used around 2000 rounds plus and since then it has been doing nothing for 6 years so i had it serviced and greased etc prior to a skirmish on sunday.   I have just installed a madbull 6.03 509 barrel and I want to get it firing around 335 340 to allow for chrono tollerances (my sites absolute upper is 350)   Wil