I found this video which i wanted to share because I think it is very helpful, not sure if it's been posted or not. [ame="http://www.youtube.com/watch?v=60zbwMYJiLI"]http://www.youtube.com/watch?v=60zbwMYJiLI[/ame] This guy explains combat effective zone, and shots from different yardage with different zeros. Not sure what ammo he used though. Hope someone finds this helpful. *The guy who uploaded the video and put the rude entry on the video is not the same person in the video, pardon that rude opener.