Well CPA that's what I've been saying all along. Nobody is arguing the "Formula" is wrong, it's just applied differently in a larger bore versus a smaller bore, due to the different area it's applied over. It should be patently obvious that if the same load of shot is put in the small bore as the large bore there is more likelihood of deformed shot in the small bore.
If you try to shoot the same shot load you can get away with a softer shot in the larger bore than you can in the smaller bore. That's all I have been trying to say all along but The "Formula" has been constantly thrown up at me saying that Wrong, but it's true & has been established for more than a century

Miller/TN
I Didn't Say Everything I Said, Yogi Berra