So i measured the not resized wing gun with a fuselage. As i figure out that if the fuselage width is 2 and the height is 2, that means its 1x1 meters. So 2 in fuselage = 1 meter in real size. So to figure out the real wing gun diameter, i reshaped the fuselage down to the inner barrel of wing gun. The size matches when the fuselage width and height is at 0.13. So that means 0.13/2 = 0.065, so the wing gun actual diameter is 0.065 meters or 65mm or 2.56 inch which is quite humongous for a wing gun. so if u want it to be realistic i suggest rezise the width and height to 0.3 with fine tuner. So 65x3=195/10=19.5mm or 0.7677 inch