well, this afternoon, the gun worked perfect, for 1 shot, then it didn't work again. So i don't think it could be a blockage because it will shoot perfectly fine every now and again. ill try to get pics soon, maybe tommorow. about the gun upgrade, it is virtually impossible to get anything like that in australia (stupid laws). i was lucky to get the tank with a gun that should work, as most of the time, the guns are disabled permanetly.