A Winchester Model P94 plasma rifle. An industrial-grade energy weapon, firing superheated bolts of plasma down a superconducting barrel. Powered by microfusion cells.
The P94 is a bulky, industrial-grade energy caster powered by microfusion cells. The superheated plasma bolt forms in a special chamber, then sent down a superconducting barrel and stabilized by electromagnetic claws upon exiting it.
Elder Owyn Lyons mentions the P94 plasma rifle when in dialogue in Fallout 3, but it is not in the actual game, being replaced by the urban plasma rifle.