Barred from legally owning or buying weapons Gal Drifters, Bottoms, No Cits and similar groups often rely on home made weapons such as clubs, chemical propelled slug throwers (Fire arms) Front loaders, knifes, swords etc.
Among these improvised weapons one can often find so called Air rifles. Weapons that use compressed air or gasses to accelerate a projectile, pressure is built up via a pump and both ammunition and gas are easily obtained. Air Guns are also sold in underground markets, Skidder rows and Skath shops on Sin 4 and similar worlds and places.
( Eric Olafson encounters a Bottom-NonCit with a home-made Air rifle in Galactic Chronicles Book VI: First Journeys)