I'm not sure if this is an original idea or not (I'm cheap), but here goes....
In an attempt to reduce the amount of rattling of metal mags, I also added a magpull feature.
Here is what to do:
Cut a 6" section of bicycle innertube. I used a 1.75" tube.
Stretch and slip the innertube over the mag bottom. (from the floorplate) It will take work, but it can be done.
Cut a 14" length of paracord and heat the ends to prevent unravelling.
Slip the paracord under the innertube on each side of the mag bottom.
Tie a knot at each end of the paracord.
Now put the knot of the paracord just below the top of the innertube.
Roll the innertube over the paracord. Do this on both sides. Roll again. While you roll the innertube the paracord should also be rolling with the innertube.
You now have a band of innertube around the mag bottom that keeps the rattling down. The loop of paracord can be used to rip the mag out, if you have to.