From what we know at this time. Mr Sawyer states in the second Dev Diary that it doesnt require ammo, but it takes time to recharge. So you can't just fire with an infinite clip, you have to strategically use each shot.
Thanks, but I meant working that rifle into this guys challenge. I guess Playing a pacifist run with a maxed Unarmed skill is the challenge. Something i was gonna do anyway when i tried a pacifist run.