Don, are you proposing, with the above, that there is are no pressures exerted against the breech by the shell head? I think two debates are getting mixed up here. Of course, there is no recoil where there is no flow.
SRH
Stan, I'm trying to be sure folks understand that pressure, in and of itself, does not cause recoil. The pressure acting on the hull base becomes a force which does, indeed, act on the barrel and action "pressure vessel," but does not cause recoil. The pressure acting on the base of the wad becomes an unbalanced force (since the wad and shot do not have enough resistance to balance the pressure force) causing the acceleration. The momentum gain will balance the pressure force on the wad base at every instant until muzzle exit.
DDA
