Virgil's rifle

Virgil's rifle is a weapon appearing in Fallout 4.

Characteristics
Virgil's rifle is a unique Institute rifle which deals 50% more damage against super mutants. It also comes with several mods already equipped:
 * Gamma wave emitter
 * Improved long barrel
 * Full stock
 * Medium night vision scope
 * Fine-tuned beam focuser

Location

 * This weapon is carried by Virgil and can be acquired from theft or by convincing him to kill himself.
 * To make Virgil kill himself: After gaining entry into the Institute, head over to the Bioscience section, go through the series of doors and into the FEV lab. Inside, destroy the few turrets there are and once reaching the room with the super mutants in glass cylinders in it, go to one of the containers there and grab the serum. After obtaining the serum, go back to Virgil and if the Sole Survivor's Charisma is high enough, convince him that the serum isn't there and that his condition will just get worse and he'll have to die. He then requests that to be killed. Afterwards, pick up the weapon from his corpse.
 * If the Sole Survivor gives Virgil the serum, he'll tell them to wait for a few days so the treatment can run its course. Eventually you'll get a miscellanous quest to revisit Virgil in his cave. He and his Protectron will be hostile and attack immediately, which also allows the aquisition of his rifle. Avoid bringing Piper along when you do this - she'll hate participating in Virgil's violent demise.


 * This did not happen in my case, Virgil was transformed back into a human after 3 days and gave me full access to his house and all of his stuff, but no rifle. It seems you must convince him to kill himself or murder him.