ΔE 15.7, loose: different enough that you should pick on purpose. Blue Steel is a little darker, much more saturated than Ironbreaker.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Blue Steel is a little darker, much more saturated than Ironbreaker.
The same difference applies the other way round: Ironbreaker is a little lighter, much more muted.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Ironbreaker on the colour wheel See Blue Steel on the colour wheel
All matches: Ironbreaker equivalents · Blue Steel equivalents