The gun appears to be angled up, towards the viewer, well the rest of the body is pointing slightly down. If he ISNT shooting directly at the camera in the game, but is instead shooting something below him (on the ground...) thats pretty wrong.
you could try lowering the top barrels (lowering on the y, not the z) and raising the bottom (once again, y not z). Its a little tricky, because really you shouldnt see the bottom barrels at all from that angle, but I really like the Gatling gun/six shooter feel it has going when you do, so maybe just find a way to fudge the perspective a little bit towards correct?
That, or just angle the chimney back a bit, I think then it would look more like he was leaning backwards and the gun would be facing in aprox. the right direction, although that might be a whole can of worms.