Just have a gunsmith lengthen the forcing cone.
When shotgun shells were first made, they used paper wadding.
And for the wad to seal they made a forcing cone for the wad to seal to prevent burning gas from escaping.
Then came the plastic wads in shotgun shells, but shotgun makers kept making barrels with the old style forcing cone.
When the shotgun fires the plastic wad seals as soon as the gun is fired.
So the need for short forcing cones isn't necessary.
Lengthening the forcing cone does two things,
First it reduces felt recoil by about 10 %,
And decreases the pattern about 10 %
With the old style, after firing the some of the shot would flatten out hitting the forcing cone, and as it passed the choke the flattened shot would just fly wildly and get lost.
With the forcing cone larger, the shot doesn’t get deformed, and keeps going in a straight line.
Between the left, and right arrow is where the crimped part of the shell goes after firing.
The highest point of the forcing cone is where the shell and wad seal the gases to drive the wad, and shot forward.
Before with paper wads it had to be sealed quickly, to keep the gasses from escaping, but with plastic, it seals as soon as the shell is fired, keeping the gases from escaping.

Forcing cone before.



Forcing cone after it has been lengthened.




I hope this helps.

jrbsr

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