Angry Bull uses the Hadron AAP-01 Short stroke bouncer kit to fix the misfeed issues with the GBB pistol. The AAP-01 Short stroke kit, or the “Bouncer”, is a set of parts that improves the feeding consistency and reduces the shock of the bolt. It comes with a Hadron Designs specific 300% upgraded spring, which works well with most buckings, and a shortstroke segment made of a bouncy material that absorbs and rebounds the bolt impact. The kit also includes a small solid tube that can be inserted into the nozzle return spring as an optional guide and bumper.