I am tempted to remove the barrel lock on a M-21 and a L. C. Smith (both 12 ga.) and shoot. Also, might ask an Eng-student who shoots, about stress/strain gauges. BTW, for those who think a M-21 is very,very long, my M-21 is 2 5/8 from face to center of hinge pin; so is my L. C.(both 12 ga.). I will also check " The Elastic Strength of Guns" by Phillip R. Alger Professor of Mathematics USNA to see if I can find a math way to calculate the amount of flex at 8000 psi.