Shootas are large caliber machine guns, no one knows how this design comes about, but it is assumed it was made out of Imperial Boltguns/Bolt Pistols as the back handle is near identical, it has also been modified to make a loud noise as Orks enjoy anything that fires a lot of bullets and makes a loud noise, though truth be told, the average Ork has a better chance at using his Shoota as a club by bashing someone head in than actually hitting anyone by Shooting it.