As Dusk said, it is entirely possible for higher voltage guns to cycle after the cut off lever has deactivated the current. This I believe is called Overspin.
On normal guns single shot is achieved by a cam on the sector gear moving the cut off lever to knock the switch out at a certain point of the cycle, i.e just after the gear releases the piston. Add a high voltage and a turbo motor, you've got yourself a 2-3 round burst of semi.
Same principle applies to the Type 89's burst mode. Every time the cam comes round it knocks an arm, which moves down a notch, after 3 movements the ar