I've seen those before, on ebay- never handled one. I don't think the guy makes them anymore. The mag slips onto the adapter that attaches to the QB'S scope rail. I'm pretty sure (Though correct me if I'm wrong) that there's a difference in height between the load port and scope rail, between the Disco and QB. Depending on price, I'd say go for it though. Maybe you'll luck out and it'll work.The BNM breech isn't too complicated- you just have to remove the old breech and replace it with a BNM breech... It's a pretty simple 15-20 minute procedure.