moses, I see the muzzles in my peripheral vision and do judge lead. On a snap shot I am not conscious of them. If I see rib and bead I am aiming my gun like a rifle and more times than not I chalk up a miss. When I focus on the target and see the barrels peripherally I hit them solidly. I just wondered what the effect of a sunken rib would be on my shooting and found out it's nothing to be concerned about.