Double springing= take 2 mag springs. Lay 1 on the work table. Lay the 2nd over/on top of the 1 on the table. Push them together so they mesh into each other. Re install in mag body. The spring tension on the follower will now be noticeably stronger. Loading each round will also be more difficult. I used 1old factory mag spring and 1 new spring from a K-Mag brand magazine. I bet 2 older ones will work just as well, when you join them together.