Choked at the muzzle or not does not make ANY difference. The pressure is dropping very quickly as the charge heads out the tube. It is always more than the pressure in the tube of the air compressing in front of the ball, along with the stmospheric pressure, which is why it actually exits the tube, but anywhere near what it was at the breech, is impossible. A blip at the muzzle end caused by a choke, will not make enough difference to be noticed and certainly will not increase the pressure to what it was when the charge first went off.
If you view any pressure curve charts for black powder (or even Pyrodex), they are all very much the same. They peak before 2" of ball or shot charge movement, then rapid decline the rest of the way out, to where muzzle pressure is minuscule in comparison, mere fractions of what it was at peak.
The early peak then rapid decline is why barrels can be tapered, sometimes to very thin muzzles.