Surefire is another alternative if you are using 5.56 or 300 Blackout. I have a couple of the 60 round mags for my ARs. The larger 100 capacity are not practical. Better to go with the dual drum.

http://www.surefire.com/tactical-equipment/high-capacity-magazines.html

Good people sleep peaceably in their beds at night only because rough men stand ready to do violence on their behalf.

Someday your life will flash in front of your eyes. Make sure it is worth watching.