I think it might be hard to nail down the top stop for any specific handgun. No real numbers. The 1911 may be close because so many different makers produce some model or variation. S&W's M&P seems to show up a lot:

http://blog.cheaperthandirt.com/top-10-best-selling-concealed-carry-handguns/

http://www.washingtontimes.com/multimedia/collection/top-10-handguns/

http://www.gunbroker.com/Content/Top5/2014-02-GunBroker-Top-5-Guns.html (by months)

http://www.guns.com/2014/03/21/gunbroker-breaks-top-five-best-selling-guns-every-category/