Nope. At least not that I'm aware of. I think that as cool as the tip up barrels are, that's also the major drawback to them if you're unable to slide the rack. I'm not sure the philosophy of that design included reloading. I think they were meant to be small, last resort guns that you drop when empty, but that's just my thought.
This has been my experience, anyway. Maybe someone will come and enlighten us both.