Pipe Spearguns

Pipe Spearguns are closely related to the railgun, powered by the same rubber loading design. Unlike railguns, the shaft is not supported by a rail which extends down the barrel. These spearguns use the mech to secure the shaft at the base, and the muzzle to support the spear tip. 

By removing the rail from the barrel, your gun becomes a little lighter and less bulky so tracking through the water is a bit easier. It also means the gun barrel can be neutrally buoyant or balanced in the water with a smaller internal diameter. 

One issue with this gun design is that without a rail to support your shaft it can begin to sag, especially in longer guns. This can impact the accuracy of shots. And because the barrel of Pipe guns are generally thinner than railguns, they can be more prone to bending under loading strain.