Gun system and accessory thereof

A gun accessory includes a main body having an upper surface having two sides, a first side wall and a second side wall extending upwardly from each of the two sides, first and second slide members provided on the first and second side walls, respectively, and a first locating hole provided adjacent the first side wall. The accessory also includes a first locating bar pivotably coupled to the first locating hole and having a first baffle and a first press plate, and a first elastic element provided between the first press plate and the main body to pivot the first press plate with respect to the main body, and in turn drive the first baffle to protrude above the upper surface of the main body.