Abstract: The invention provides a barrel for a gun having a portion comprising a substantially transparent material. The barrel can be made of any substantially transparent material including a polycarbonate or glass, such as tempered glass. The barrel is coated with a substantially transparent material to add hardness, which provides scratch resistance, and prevent deterioration of the substantially transparent material. A barrel assembly is constructed by attaching the barrel to a gun housing, also called a barrel cage, comprised of a stiff material, for example metal such as aluminum. In another aspect of the invention, an expansion chamber is provided having a housing with a portion comprising a substantially transparent material, such as a polycarbonate or glass, such as, tempered glass. The housing is coated with a substantially transparent material to reduce scratching and absorption of pressurized gas into the transparent material.