Agree with your 0.800", 2-p. I used one inch only as a scale place holder. Certainly the barrels are not static during discharge and shot passage. They will, in fact, have reached maximum movement velocity at shot exit but not maximum movement.
The "fly in the ointment" of barrel convergence regulation and barrel flip regulation is the individual shooter. Factory made regulation is approximate unless fired by the shooter.
Using 2-p's numbers above, we see that barrel movement is expected to be about 5/16" for 30" barrels: 15"/ (40 yd X 3 ft/yd X 12 In/ft) 1440" = bbl move/30"; bbl move = 15" X 30" / 1440" = 0.3125" + 5/16". I suspect "average" is generally close enough.
So, unless you have shot patterns for the guy regulating the barrels, you are sorta getting "luck of the draw."
DDA
