And yet the porting on the top barrel is not the same as the one on the bottom barrel. I shoot sporting every week - I do not change chokes, but, as required, I may change which barrel. Since I only shoot light target loads in these guns, muzzle rise is minimal at best.
Seems funny to me that field guns typically do not come with porting, yet the guns are lighter, you're usually shooting heavier loads - which would mean more muzzle rise. If there was ever an argument for porting, it would be there.
But that's OK, these discussions are mild and kinda fun.
And sorry, Zippy, I'll give you a smidgen on porting for muzzle rise, but I won't give you anything about it reducing recoil - Heavy gun plus light load in a properly fitted gun makes that happen!....