After reading this thread yesterday I decided to get that gun.
When I entered the buildning, and that first robot came up to me, I talked to it, then I took half of the tour, the first robot came to me and said I should leave, but I took the tour for a bit longer, then I was going on my way out, but my time was out, so the first robot, with everybody else started shooting at me, with Sentries and everything

I just run away cuz I hate Sentry robot things, but Boone just smashed it with very few Machete swings, so I locked up the avarage door where the Fiends corpses are, walked on, to the very hard lock door, opened it, and a sentry thing came, Boone stormed in, took the Sentry out, and I walked over to that place where the gun is. "What the hell?" Thats what I said, cuz the gun, it wasnt there!! So then I remembered what many companions do at Vault 34, so I checked Boones inventory, and there is the gun, just like that! :celebration:
Bring Boone to Repconn if you want the gun without do lots of other stuffs to get it

You could problary use some other companions who usally pick weapons up that your are looking for but suddently they arent there.