Captain Paul A. Curtis explains it quite well in his 1934 book- If you don't have a copy, e-mail me through this website link, and I'll reply with a quote from him on this.
The other gent that commented on the "pitch always being measured from 28" barrels-- OK- answer me this-- Are All shotguns made today, or even the ones of yesterday, with 28" barrels. The pitch degree or "stand-off" in inches from a plumb surface set to a 90% base angle will vary with the barrel length- which theory I proved with my L.C. Smith with 2 sets of factory barrels of different lengths. RWTF
