Plasma rifles or plasma casters are high-tech weapons which find numerous applications in military and industrial fields. They fire superheated bolts of plasma powered by either microfusion cells or heavy energy cells. The bolt forms in a special chamber, which is then sent down a superconducting barrel, propelled by, and in some models stabilized by electromagnetic claws upon exiting it.
Initially, the weapon was a bulky, industrial plasma caster, manufactured by Winchester Arms; while it performed admirably, it was expensive and required specialized training to use. However, later developments for the US Army would lead to a more compact design that was cheaper to produce and easier to train for, perfectly suited for urban warfare.
Regardless, all types of plasma weapons have a common feature: when a Critical Hit is delivered, they can literally melt down enemies. While most industrial casters aren't powerful enough to dissolve bones too, subsequent models have no problem converting the target into a puddle of goo.
The multiplas rifle (a portmanteau of "multiple" and "plasma") is based on the urban plasma rifle design. It is a sort of plasma shotgun, firing three rounds of plasma in a volley, at the cost of a massive drain on the microfusion cell.
The multiplas rifle is a plasma-based weapon, bearing a similar appearance to the plasma rifle. It is most easily distinguished by its three plasma barrels at the rifle's tip, which fire three very destructive rounds of plasma with very little spread. It uses one round per projectile, for a total ammunition consumption of three rounds per trigger press. Like most plasma-based weapons, the multiplas rifle causes a large green burst of plasma upon firing which partially obstructs view. In addition, the plasma bolts travel at a slow rate, resulting in the need to lead the shot.
Due to the fact that it fires three plasma bolts at once, it can score a Critical Hit for each shot outside of V.A.T.S. This attribute allows it to sometimes hit a target for a huge amount of damage per shot.
The multiplas rifle is the plasma equivalent of the tri-beam laser rifle, as it fires three bolts of plasma per shot.
If the bomber is allowed in during the Birds of a Feather quest, the rifle will be part of the ordnance that gets destroyed.
If used to attack the ants in the quest Ant Misbehavin', it will cause them to explode.
In the Fallout: New Vegas Official Game Guide, there is a piece of concept art for a triple-barreled mutliplas rifle. The barrels are yellow-tinted, there are extra wires running along the side and cell basket, and there is also a different grip than the one seen in the game.
Within the game world object files, the rifle's model is labelled as "unique". There also exists an unused "non-unique model", which suggests that the weapon was originally intended as a unique variant of a usable standard version within the game.