Recoil

From wiki.soldat.nl

Simply put, recoil is the "kick back" of a weapon. In Realistic Mode, recoil forces your cursor higher upon every shot you make; avoiding this is quite easy since all you need to do is fire in burst shots of 3 or less. The only weapons in Realistic Mode that do not have recoil are the Combat Knife, Barrett M82A1, Grenade, Cluster Grenades, and Flamer.