A few thoughts on this theory. "IF" the gun is tight & on face & the barrels & cartridge come back together there should be no "Hammer" as the parts are already in full contact with the breech. "IF" on the other hand the breech springs away giving a gap & then springs back forward till it hits the barrel breeches this could account for the imprint on the breech face just as well as if the barrels hit it.
A good test of this theory is to remove the bolt from a Browning A-5 & fire it & see if the barrel & bolt recoil together as they do when locked. You can do the firing though, I'll Pass.
The other thread incidentally is referring only to the rotational portion of the forces & has nothing at all to do with this axial thrust.
"IF" everything worked as in your theory then you should never see a frame cracked at the bar & breech junction as there would be no force there.
