Abstract: A paintball gun comprises: a body defining a gas storage chamber for connection to a source of pressurized gas, a breech into which paintballs can be loaded, and a hammer chamber; a bolt slidable in the breech and having a bolt inlet port; a hammer slidable in the hammer chamber and connected to the bolt; and a poppet valve comprising a valve body defining a valve inlet connected to the storage chamber, a valve outlet connected to the breech, and a blow back port connecting the inlet to the hammer chamber, and a valve member slidable in the valve body and movable between an open position, in which it allows gas to flow from the storage chamber through the valve inlet to the valve outlet, and a closed position in which it closes the valve, and a pair of magnets arranged to bias the poppet towards the closed position.