Moses has it correct - you have to measure the angle, not how far the muzzles are from a wall. Different length barrels give different distances from the wall. Basic geometry. I built a tool that I can put on the rib which extends backwards over the stock. A plate extends down at a 90 degree angle and I can measure the pitch in degrees with a protractor. This plate is clear and I can also use it to measure cast at toe and heel. Putting the gun upside down on a level table and measuring the pitch works just as well.
For most men 4 degrees of negative (down) pitch is about right. Women usually need more negative pitch - 6 to 7 degrees. The Brits figured this stuff out over 100 years ago. The subtle points of stock fitting are not for everyone, but it's part of the hobby that I enjoy. Making my guns fit me makes them easier to shoot well and more comfortable.
Regards,
Jeff
