Not sure if this should go here or handguns. 
Anyway there seems to be a lot of questions about this subject matter. This article does a pretty good job of answering some of those questions, especially gear related. The Ultimate Guide to Pistol Mounted Red Dot Sights - Tier Three Tactical
As they mention in the article, if you really want the details of all of this check out this study done by Aaron Cowan of Sage Dynamics.
http://docs.wixstatic.com/ugd/7dc128_b5f92f089b1842e791d3a95199590510.pdf
Anyway there seems to be a lot of questions about this subject matter. This article does a pretty good job of answering some of those questions, especially gear related. The Ultimate Guide to Pistol Mounted Red Dot Sights - Tier Three Tactical As they mention in the article, if you really want the details of all of this check out this study done by Aaron Cowan of Sage Dynamics.
http://docs.wixstatic.com/ugd/7dc128_b5f92f089b1842e791d3a95199590510.pdf
