IMO the heavier the powder x's shot load the more benefit you get. Look at the 12guage with 3" or 3.5" chambers Mossberg's that are marketed for waterfowl, turkey or slugs in a 500 or 835...notice that the ports are angled off to the side and angled up at about 45*'s to help control the muzzle jump.
Mossy's old 695 bolt action 12 guage slug gun had ports too, even though it weighed 9+ lbs, anyhtig that could help wiht the hevy ammo's muzzle jump and keep the stock's cheel piece off of beating up your face as much as possible.
Lots of Trap guns have ports too, only for the long strings of rounds shot at one time in competition.
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