Tornado brushes are intended for use on smoothbores (shotguns) or cylinder charge holes. You will notice that the edges of the wire contacts the bore, not the end of the wire bristles. The design will not properly clean to the corner of lands and grooves like the standard bristle brush.
In answer to you first question, a stainless brush will not normally harm a modern steel barrel. However, that said, I would not think of using one on a match-quality barrel.
On early mild steel (blackpowder days) gun barrels, a harsh stainless brush cleaning will put noticeable wear the rifling lands within a few dozen strokes. I've been guilty of using stainless brushes on badly rusted and fouled bores, but that is a desparate last resort before acid cleaning.
HTH
John
