I was discussing this phenomenon elsewhere with a fellow sxs shooter. The only reference I could find to it was in McIntosh's "Shotguns and Shooting" (p. 104). Nothing I could find in Brister, Zutz, nor in 3 books by Gough Thomas. MM says it causes a sxs to shoot somewhat low. Comments from the group on how big an issue it is for sxs shooters??