Thank you very much for the fast reply Larry. Also, thank you for recognizing & addressing the matter in the future. We appreciate your consideration!
As for the demand & the why, take a look at these two threads over on brianenos.com 's exclusive 3-Gun forum section:
http://www.brianenos.com/forums/index.php?showtopic=32804
http://www.brianenos.com/forums/index.php?showtopic=25632&hl=
In brief; our sport focuses on the AR-15. Scoring is a little like the Olympic Biathalon sport: you MUST shoot BOTH accurate AND fast. Because we use the AR-15 so much, and most all magazines are only 30 rounds, its typical to have stages that are just over 30 rounds, thus forcing you to use up extra time doing a reload. If you have a 40 round mag, you can often skip that reload.
How much time will a 40 round mag save you? Though it depends on the stage, it could be from 2 to 5 seconds. DId you see some of the Biathalon finishes? Some of those guys won by a nose (they won by inches over the competition). In that case, 2 seconds is a very very long time.