|For an overview of plasma pistol variants in all games, see Plasma pistol.|
“This Glock 86 plasma pistol has had its magnetic housing chamber realigned to reduce the drain on its energy cell. Its efficiency has doubled, allowing it to fire more shots before the battery is expended.”— Fallout 2 description
The ammo capacity is doubled compared to a regular plasma pistol. It still consumes one small energy cell per shot, however.