ΔE 22.4, loose: different enough that you should pick on purpose. Ironbreaker is noticeably darker than Shining Silver.
Can I use Ironbreaker instead of Shining Silver?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Ironbreaker is noticeably darker than Shining Silver.
Can I use Shining Silver instead of Ironbreaker?
The same difference applies the other way round: Shining Silver is noticeably lighter.
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.