The Churchill method as I understand, suggests that to correctly modify a stock one should use a pattern board and apply a formula. I believe it is: move the stock 1/16" for every 1" off based upon the center of your pattern shot at a mark 16' from the shooters eye; hence The Rule of 16s.
I assume that the bend is measured at the butt not at the nose or the cheek or the comb. So if your pattern is 2" to the left, the BUTT needs to me moved 2/16" to the right creating cast-off for a RH shooter.
My question is where is the measurement made?

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.

All bending is measured from the CENTER of the barrel rib. A string looped over the front bead, laid "over" the center bead, and then extended taunt to the heel of the buttstock. Measure down from the middle of the string to the Center of the buttstock heel. That is your starting point. I use a six inch scale with large graduation marks. Since this is not exact(no closer than +/- .030(1/32") you should get close enough for your needs.

I would caution you however....changing point of impact via bending is not an exact science. Some people need more or less of the needed bend due to physical body build of the intended shooter. Hugh got there first in answereing....I would never argue with an English stockmaker!!!!

Hi Mark,
You're on the right track but have several important details wrong. First, it's 16 yards, not feet. Second, your eye, not your butt, needs to be moved 1/16" for each inch of correction movement.
The ratio is established between the 16 yards to the target and the 1 yard(approximately) from your eye to the front bead or muzzle. Therefore, to move the impact 1", the rear sight(your eye) needs to move 1/16", in the direction you want the impact to go. Also, it is important to mount the gun and shoot quickly, no correcting or aiming. You're trying to correct how the gun fits you, not learn if the gun shoots straight. That should have been done first. You also need to have established a proper and consistent mount, beforehand.

Thanks to all above who have replied. Jim you are right about my error, I meant to say 16 yards not feet (I'm still looking for the "yard" key on my keyboard).
Yesterday, I shot the gun at the patterning board at my local SC range. Both barrels shot spot-on; printing exactly on top of each other. Yes, my mount is consistent. The hits are all exactly in the same place (2" left) indicating the need for a slight cast-off of the stock. No surprise since I'm right-handed and the stock is cast neutral. Now I have learned that the it's the point of my EYE on the stock that needs to move 1/8"; the butt of the gun will move slightly more.
Thanks again.

You got it, Mark!

Don'T know this one . Stock measurements need to be discussed with a good shooting instructor or a good gun fitter.Its not an exact science and a lot of people made a lot of money writing books with their methods and "formulas" . If you read Greener for example , he will tell you how good his guns were but at the same time put down other makers. If it works for you then fine,but if these methods were that good every gun maker and gunsmith in the world would know them by heart and use them.

This might be helpful.