Conservation of momentum requires that the gun have a rearward velocity proportional by the ejecta weight vs the gun weight to the forward velocity of the ejecta. That requires that the gun experience an acceleration proportional to any experienced by the ejecta. Total recoil of the gun is easy to determine for both momentum and kinetic energy. The fly in the ointment is that we have, so far, no way to know what the shooter actually senses. It could be peak momentum, peak energy, displacement, acceleration, etc. It is based on pressure only in that pressure is causing acceleration, not pushing back on the gun.
All involved in this discussion need to read "Sporting Shotgun Performance" by Dr. Andrew Jones. Constriction was about it for choke effect. The gem of his book is, however, a computerized method for pattern reading and analysis, statistically valid analysis. To my knowledge, this is a real first. Anyone taking the time and effort to shoot patterns owes it to himself to read this book.
DDA
