I don't think there's a hard and fast correlation. "Consumes n ammo per shot" is more like the game's way of telling you that there's some special ammo-related magic at work, like with eTech guns, which eat 2 bullets to be able to spit out 1 energy projectile, or with Torgue guns and their gyrojet projectiles. With shotguns, normal ones consume 1 ammo unit to deliver x number of pellets.Well, fuck me, I recently took this quest at lvl 50, but somehow it glitched and I ended up without any of the rewards (of course I was going after the Heartbreaker).
I assume there's no way to replay the quest without starting over with another character, right?
BTW, might be a silly question, but I was thinking about this today: the weapons that "consume n ammo per shot", do they actually fire n bullets per shot?