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Railguns are unique in the sense that they have an extended "rail" incorporated into the aluminum barrel for the full length of the shaft. This rail supports the spear the full length of the barrel and continues into the muzzle. The rail barrel tube is also much stiffer and stronger than a normal tube because it is thicker-walled and has a slightly bigger diameter.

The integrated rail adds further strength. Rob Allen also uses aircraft-grade aluminum when the barrels are extruded. This gives the barrel even better strength and stiffness, enabling it to handle strong rubbers and be used in longer lengths without flexing. It is stronger and stiffer than wood of the same diameter. The result is a gun that is remarkably light in the water, enabling the spearfisherman to relax in the water and subsequently reach far greater depths in the hunt for a wide range of target species.