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.
This plasma rifle is a lightweight urban warfare weapon created by REPCONN Aerospace for the US Army based on engine parts from the failed Z43-521P - "Green Bean" plasma-powered rocket. Like the AER9 laser rifle, it uses a microfusion cell as its power supply. It taps into the cell, essentially a small fusion reactor, to produce a toroid of plasma that is ejected down a superconducting barrel. In contrast to the Winchester P94, it does not have the electromagnetic claws.
Any regular plasma rifle will set Harold on fire, but like all unique weapons, Harkness' does not. It will, however, still detonate gas leaks like most other energy weapons.
This plasma rifle is unavailable after completing "The Replicated Man" by giving Dr. Zimmer the android component. It is still possible to receive the rifle and complete the quest this way, but it must be obtained before giving Zimmer the component.
It can be obtained very early into the game by traveling straight to Rivet City and starting the quest there, because it only requires talking to a few doctors in Megaton and Rivet City and then Pinkerton. One major drawback is the availability of microfusion cells and plasma rifles at this stage of the game.
At full condition, it is one of the most valuable weapons in Fallout 3.