When you take a PDW2000 and put it in single-fire (semiautomatic) mode and pull the trigger rapidly, your aim is kicked upwards drastically.

If, however, you put the gun in three-round burst or fully automatic, there is little to no upward "kick" at all. Even when you pulse the trigger to fire only one bullet at a time, there is very little kick. This is inconsistent with the gun's behavior in the semiautomatic mode.