shooting tank barrel

This is a shooting barrel for Bavaria_3d tanks tank/contest. it shoots 6mm bbs which can be 3d printed. You will need a normal spring from any pen and a m3 bolt which could be 3d printed. This model only includes the barrel and not the rest of the tank. The shooting mechnism is widely spread so i dont really know who to give credits, but i first saw it at jaatinen3ds models. The range depends on the spring. mine easily shoots 10meters