A long time ago I decided o goose hunt with a nice 6 1/4# Italian made 12 ga O/U w/ 3" chambers. The forcing cones were european as well as the bore diameters(more like 0.715"). 5 shots w/ 1 7/8oz 3" loads left me w/ a bone bruised shoulder. Couldnt shoot anything bigger than a 22rf for 5 months. Now the biggest thing I shoot is a 375 Ruger on a Rubbermaid/Tupperware stock. I dont shoot more a half dozen or so rounds from a bench at a sitting. The biggest problem i have w/ bench shooting is my rt hand knuckles and bolt handles or the pistol grip biting my left hand. In the past I had some primer problems so I know I dont flinch when focused on shooting, at least not all the time.. BUT, I have found myself flinching and blinking when trying to shoot a crow w/ a Ruger 204. Your mind definitely controls your reactions.
