It's not that hard to grasp, is it? My old man used to be able to tell with some degree of accuracy whether or not a gun was too powerful, too weak or just right, just by counting the affected pages of a shot phonebook.
Problem these days, some don't consider you a 'proper' airgunner unless you've got a PCP, bipod, a few hundred quids worth of real tree, the latest boots & can hit the wings off a gnat at 50 yards...
I get what your saying mate but to me it just seems a little dodgy no offence intended!!