How would a Gunzerker dual wield bow's? What role would a bow play?
For this reason, the closest they'd get would be a crossbow. And even then, I don't see this happening.
Going by manufacturer, I can't picture any of them making crossbows. Jakobs, Maliwan, Hyperion, Tediore, certainly not. *Possibly* Torgue... maybe Bandit, making some kind of ragtag crossbow.. but I just don't see it.