I theoretically you could get a barrel ring bulge. I'd tend to start with IC, pattern it, then work up to modified. If steel patterns OK with mod, I'd leave it at that. It's possible the new chokes are labeled for steel, unlike the older ones which were labeled for lead.
I have a older Win 101, the first ones they ever built with the all new Winchoke back then (1980) Even with IC and mod it shoots really tight with steel, so I mainly use skeet and IC for all steel from #3to BBB. It would always kill reliably if the nut behind the stock weren't so loose!
Check with your booklet. Or if the choke states "steel only" or "lead only".... or something along those lines.
Also if you shoot an email to Winchester i am sure they would answer your question.
But one thing to do is go PATTERN your gun. Because your full choke might throw the shot low and left. Where you mod, IC will have a more consistent pattern. Draw a 30 in circle, aim in the center, and shoot. See where the bulk of your pattern is... with any choke u want to use. Then do again at other distances.
Then what I have done (might be going over board).... I will find out how many pellets are in each shell....(you can find this info on the internet.... 1 oz of #2 in 20 ga. is XXXX of pellets)..... then I will count how many I have in that 30 in circle. I like to have 60-65% of the pellets in that circle with more the better.
Yes when I tested out my beretta extrema 2 with different chokes, shells, and pellet sizes..... my friends thought I was nuts. I will have to say it has worked out good for me because now I know what shoots good out of my gun and at what ranges.
Keep in mind that all chokes are not created equal. In many of the guns targeted at waterfowl a full choke is in reality modified choke to accommodate the use of steel shot (modified choke that throws a full pattern with steel) Depending on the manufacturer I have seen 112 ga full chokes list as being .695, .700 and .710 diameter One companies full may be anothers improved modified or modified.
Sx3 is a modern era shotgun made during the requiem use of steel shot for some species. If it is a factory choke it should be steel safe unless marked otherwise. You should be able to find the constriction of factory choke on line. If it is not factory then you need to refer back to the mfg.