The ADL was replaced by the SPS. The ADL had a Blind box mag inside the stock. So it's a hollowed out stock, with a aluminum box inside, and then the spring. You have to load the ADL from the top and to unload it you have to cycle your bolt and expend the rounds one at a time. The BDL has a metal base under your stock that is all one piece to your trigger guard. You press the button inside your trigger guard and the bottom drops out expending all of your rounds.