Abstract: A hop-up device for an airsoft gun allows a user to adjust the tension applied to a BB during the chambering of the BB in the airsoft gun. The hop-up device has an adjustable tension adjustment sleeve configured to constrict a desired amount around the BB. The tension adjustment sleeve provides tension on the BB when the air nozzle is seating, or chambering, the BB in the bucking lips of a rubber bucking prior to firing. By adjusting the tension adjustment sleeve, the user can increase or decrease the bucking lip tension on the BB to reduce or essentially eliminate the adverse effects from manufacturing tolerances, wear, and the like. These adverse effects can cause double feeding of the BBs, jamming, inconsistent firing, slow firing, midcap syndrome (the feed spring in the magazine is too strong and forces BBs against the air nozzle with excessive force), and the like.