jojo, I just downloaded your model to give you better feedback.
IMO, it looks good on the screenshots.
The tube doesn't look like a good way for a bullet to hit any target at all.
The model itself has about 70.000 Vertices, while it shouldn't have more than 1000 or 500.
It seems that you used a program like blender and applied to a relatively lowpoly model several times the multiplyer, and that's the reason why the 'tube' looks more like an oval.

In case that you still have the low poly version, maybe, that one could be used in a game.
The version that you uploaded is not suitable for games.