The video you posted is very interesting Shotgunlover, and if anything, I think it tends to verify Miller's theory of tapered bolting surfaces having a tendancy to be cammed open upon firing.
There would be a big difference in a sustained force of weight being applied to the barrels of a gun clamped in a vise, and the milliseconds impulse produced by the dynamics of firing. It would seem that the top lever spring returned the bolt and top lever back home within a fraction of a second in the video. One could imagine that it could actually pop clean open with enough camming force and a weak enough top lever spring to be momentarily overcome.
I have never experienced this in my own L.C. Smith's or my one and only Ithaca NID, but watching your video suggests that it is indeed possible. I can't recall the exact loads Buck Hamlin was using for his "Nuclear Loads" in his Damascus testing, but I am sure they were way above any normal sane proof load by the time the L.C. Smith in question was blowing open. It was even more impressive that he had lengthened the chambers in this ratty, rusty, pitted Damascus gun so he could stuff even more powder and shot into it. It would be cool to see an ultra slow motion video of those tests.
