Nice idea for a weapon, although I think the magazine needs a magazine realese button or latch, so the magazine has to move forward and the pistole grip as it is now would be very impractical. I would recommend you to take a pistole grip similar to the pistole grip of the german MP40 or the M1A3 carabine. You could also take a folding pistole grip although I think that would increase the production costs for no real benefit.