Interesting thread.
According to my reading, the "issue" with the 20 ga. version of the Flues is not chambers bursting, but it's lightweight frame cracking. Agree. There seems to be some debate out there as to whether the cracked frames are the result of excessive "pressure" or excessive "recoil". It is from pressure. The backthrust of the shells is due to pressure and is contained by the standing breech. The force on the standing breech is carried to the action bar around the angle between bar and standing breech. The greater the radius of the corner, the less the stress riser effect. When a force canges direction, it tends to "pile up" as sharpe corners. Note that high pressure guns, (think double rifles) have a good radius and a reinforcement lump of metal to help resist the "pile up" of force on the corner. I, quite frankly, have not found a satisfactoty explanation of the difference between pressure and recoil, if in fact there is a difference. Pressure is the result of the propellant producing gas faster than the gas can flow away from the "fire." The pressure is equal in all directions. Recoil is due to conservation of momentum and is the result of the weight of the ejecta traveling down the barrel. The action feels recoil on the rear where it mates to the stock.
I'm at the point now where I believe that I am over-thinking this whole matter of chambers, cones and pressures. I need to start enjoying this gun with my low pressure 2 3/4" reloads, instead of continuing to worry about it. Good plan. However, understanding is a good idea also. If you are still unclear as to recoil and pressure, post back.
