If you use steel shot in any gun, be it modern or not, you must use a plastic, steel-shot wad. Normal wads lack the strength and thickness to keep the steel or iron pellets from scraping and cutting the bore - chromed or not. You must also use enough normal wads to keep the black powder from melting the base of the wad and coating the bore with plastic.
: Another problem with steel wads, is they are thick, hard and take a very heavy load to make them open up to release the shot. This means even a heavy load will probably make very small patterns, but steel shot does not have the energy to kill at long range, where small patterns pay off.
: - suggestion - One thing you might do, is to find a fairly thick poly sheet, or some sort of plastic or other fibre that has strength against compression, yet is plyable enough to wrap it into a tube shape. Load your powder and base wad about 2" down the muzzle, then push in this tube of whatever, fill it with steel shot of whatever size, then put a thin "B" wad over it. The thick 'material you found' may protect your bore. It's all about experimentation.
; Small patters on the paper are great as they give long range shooting posibilities but steel shot slows down so quickly, it is useless for anything past about 40 yards. Have fun trying to find a load that works.