The purpose of the buffer isn't to mitigate recoil. It's to counter balance the system of gas, mass & springs running the gun and to make it run reliably. The H2 and H3 were developed by Colt to ensure proper operation of M4, M4A1 & Mk18 guns on semi- and full-auto. The bolt speed you get on 14.5" and 10.3" guns, combined with the greater mass of the SOCOM profile barrel (AND suppressors), leads to bolt bounce and overrunning the mag spring. If you don't counter that with a heaver buffer to slow things down, you get trouble.