Nathan Joseph, 22, of no fixed address, but formerly of Medway Avenue, Grantham, turned his gun on an opponent and swung it like a “baseball bat” after he was shot himself during a game at the Ancaster Karting and Paintball Centre.
The attack left his victim with multiple skull fractures and in a coma for five days, Lincoln Crown Court heard.
Jon Dee, prosecuting, said Joseph knocked his opponent to the floor with a first blow to his forehead.
Joseph, who had earlier boasted “we do things for real in London, we’ll slice you,” then continued the attack while the 30-year-old man lay unconcious on the floor – repeatedly striking him to the head with the butt of his paintball gun.
Joseph was only prevented from continuing the attack by staff and other players and fled before police arrived at the karting and paintball centre in Ancaster.
The court heard Joseph had signed in under a false name after attending the centre with a friend and two youths. Two other groups including a stag party were also at the centre.