I do not have figures for what the closed cell pressure of a typical shotshell powder charge would produce, but I sincerely believe that if the shot charge "Failed to Move" the chamber of any ordinary gun would be "Blown to Smithereens".
Burrard gave some figures on this using the British bulk powder Smokeless Diamond, 33 grains = 3 dram measure.
This 33 grains if confined to a length of 1" of typical 2½" 12 gauge cartridge case would produce about 30.3 tons per sqin pressure. The pressure necessary to burst this typical chamber of good barrel steel having tensile strength of 40 tons per sq in would be 13.4 tons per sqin. Normal pressure for this load would be 2.8 tons.
Based on a 20 ton pressure yield strength (bbl would bulge, but not burst)it is necessary to go to about 4" before the strength of the steel excedes the maximum possible pressure capable of being generated.
All of this is based upon uniform pressure rise (No obstructional effect) for the 33 grain charge in that volume in which to expand.
This would tend to indicate that no ordinary gun could withstand a normal powder charge "IF" the shot failed to move.
This is WHY Burrard so strongly recommended "NO" shell be fired if it's "Loaded Length" allowed it to extend into the cone.
All other things being exactly equal even an extra deep crimp, requiring more force to open it can cause a drastic increase in pressure. If the loaded shell extends into the cone the opening of the crimp can be retarded causing an increase in pressure.
Max pressure is reached just after the shot begins to move & immediately begins to fall. As long as there is enough clearance for the crimp to open normally one would not really expect an increase in this max pressure. What one might well expect is a very slight slowing of the fall as it goes through the reduced dia. This would not be picked up on a normal pressure test which records only the max. It would show up if you had a trace of the pressure curve.
As to recoil the "Actual Recoil" is based solely on the mass ejected & the velocity at which it is ejected. I am at this point totally inclined to believe this amakes up about 98% of "Felt Recoil" with the remaining 2% composed of burn rates, cone shape, bore dias etc, etc, etc being of such small magnitude as to be undiscernable by Mere Humans.
There are numerous effects which can cause one to "Perceive" he has been "Kicked Harder" when in fact he has not. An example is wearing adequate ear protection can seem to "Take the Sting" out odf a "Hard Kicking" gun, but of course putting muffs over your ears does nothing to reduce either recoil or kick. An obnoxious odor from a particular powder could have a similar affect, but would not actually change the kick.
It is quite easy to get an idea in ones head, but until proven otherwise, Paint me Skeptic.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra