Banshee's pleased that you want the heavy Bow in his workshop. "Good," he says. "Real good. Uh. Problem is, though, lock on that case is real secure. Haven't opened it since we won the war against Ghaul. Not sure I even know where the keycodes are."
He contemplates a moment. "Well. That's all right. We can reverse engineer 'em. I'd say crack the glass, but…" He trails off. There is an ominous look in his eyes. "I don't recommend crackin' the glass."
He gives Ghost a number of diagnostics to generate a new keycode, and then sends you on your way.