The big issue with steel vs. lead chokes is that the "lead only" choke is of softer steel and sometimes thinner steel. "Bridging" of shot can occur when larger shot runs shoulder to shoulder through a tight choke and can bulge the choke due to the resistance to compression of steel shot resulting with damage to the choke and threaded portion of the barrel. Large lead shot out an old double with tight chokes can and has bulged the barrel at the constriction, notably old Super Fox and Ithaca NID doubles. #7 steel for dove would probably be fine with an open lead "only" choke. I wouldn't have a problem shooting #7 steel out of an IC choke in my 870. I've seen reports of shooting steel shot out of older pumps not harming barrels with less constriction than modified and steel shot no larger than #3 without issues. OMMV.
Steel shells typically have higher velocity than comparable lead loads. Steel #7 at 30 yard ranges would probably do the deed, especially early season birds. I scanned the Advantages reloading manual and for 3" 30 ga., the loads were all 3/4 oz. and they were moving from 1350 to 1500 fps One load of #7 was 1150. With difficulties bringing down late season doves, taking long shots with steel would be a no go. I'm just glad I don't have to use it for dove. Gil
I think most people who have to use steel, use #6 for dove. Usually you go up 2 shot sizes for steel vs lead to get similar performance. I think you are picking up one sorta positive of steel, and missing alot of negatives. Also if you bite down on steel shot left in a breast it will probably hurt.
Long as it flies at 1400fps or faster it will kill just fine. Speed kills with steel. Two sizes larger as a rule for kinetic energy. #4' steel will have the same killing power as #6 lead. It takes a little larger pellet to weigh the same. I've killed every bird you can legally kill in North America with steel shot with the exception of turkeys no problems. Todays modern steel is pretty lethal and pretty close to lead in performance. It will pattern better with more open chokes. If you are gonna shoot a bunch of steel I would recommend you try several different load choke combos and pattern your gun see what your gun likes best