I'm with Scott on this ATN is junk. I currently have a Bushnell, Eotech, and a Nikon mounted, on a .411JDJ 12 inch Contender, a S/W 657, and a .41GNR#2 14 inch Contender. Haven't had a bit of trouble with any of them. BTY the .411JDJ which has the Bushnell is a full length .444Marlin necked to .41 caliber. It is a real hand full. The Bushnell has not missed a beat.