Churchill's description was based on his 25" bbld gun and square on stance.His guns also had relatively short stocks and significant cast,he himself was also short! The correct procedure if you want accurate results is to mount the gun normally and have an accomplice mark the point directly under the eye on a piece of masking tape alongside the outside of the stock. Measure the distance from eye to bead, this becomes D1 ( the sight radius)The pattern plate should be 16 times this distance FROM THE BEAD. Then 1/16 inch movement of the eye will equate to 1" movement of the pattern centre. It may sound a bit pedantic but as guns and stocks get longer, particularly if you are fitting a long barreled , gas operated sporting clays or waterfowl gun the error will begin to stack up.I'm currently extending a Browning Mag 12 by 1" for a tall (6'4")
client which will have a sight radius of 46.5" when done. He will need to stand 22yds from pattern plate (D1+D16/ 36)to get an effective 1/16th eye movement for 1" impact change. Hope this helps clarify.
