The SKB's are not Miroku-made guns, but the Browning website says steel is fine in all of its Japanese-made guns.

I believe all the Ithaca-imported SKB's had chrome-lined bores. Not positive about the later ones. But I have shot steel through a Model 100 20ga with chokes no tighter than mod. Might be best to stick with mod or more open, for no other reason than possible patterning issues with steel through tighter chokes.