Measuring pitch in the usual manner: butt on the floor, top of breech against the wall, measuring how far the top of the muzzle is away from the wall(in inches) will give you varying numbers, depending on how long the barrel is. While degrees might be better, not many people have a five foot protractor. All of which tends to prove out my thought that the numbers are mostly useless. Make the butt give full contact with your shoulder pocket and recoil will be felt least.
Jim, Yes, but.
The "correct" way to measure pitch is as rabbit discussed above. The "angle" of the pitch. That is certainly as the English would do it. But American stockmakers have discussed pitch for many, many years in inches the muzzle is away from the wall when the gun is set on its butt squarely and the receiver at the bottom of the rib is against the wall. And, that measurement should be taken at 28". (Yes, negative pitch is the same as up pitch. Probably need a short wall to measure that.)
As you correctly point out, taking the measurement at the end of the muzzle will give different readings for the same pitch (angle) with different barrel lengths. Thus the standardized 28".
If a gun slaps you in the face (assuming the LOP and cast are ok), put a washer under the top screw holding the butt plate or recoil pad and see what happens. I have learned that pitch is extremely important to taming recoil. Less important, but also an issue in mounting the gun.
Regards, Jake
