The door jamb 90% angle trick ONLY is valid if your framing square (invented by a Massachusetts blacksmith in 1824- from Framing-ham no doubt) tells use the door jamb is dead nutz plumb. I've done baggo volunteer carpentry work for H4H on renovation of older houses- wood moves with weather and over time, so if your framing square tells you the jamb and the floor or sill plate are at a true 90%, then you have an accurate way to aproximate the pitch- and the longer the barrels with the same stock, the lesser the pitch-
ie: My older 2E Smith- original 30" barrels will show DAC of 1& 5/8" and DAH of 2 & 1/4"- it was a live bird gun-still is today-, but owner sent it back to Fulton in 1927 and had a set of factory Nitro 32' BARRELS WITH FACTORY VENTILATED RIB fitted- 3" chambers, reinforcing yoke and Full & Fuller chokes- so, if I measure from the wall to the top of the ventilated rib, I get a slightly different reading a than if I measure to the top of the muzzle(s) a la Murphy's Law of Pitch measuring--
I am very accurate with my measurements and also construction nomenclature- ie" In the Stephen King- Peter Strauss novel "Black House" our "State of Mainer" author mis-used the stair layout terms- he got it bass-ackwards- treads are what you put your feet on to ascend or descend, the risers are the back than enclosed the stair carriage on finished work-and the nose is the rounded overhang of the tread as it is installed on the carriage-- but, other than that, it was still a good read, if you like WI bikers and craft beers--
