ΔE 23.9, loose: different enough that you should pick on purpose. Chainmail is noticeably lighter than Ironbreaker.
✓ Herrick Games paint comparison chart lists these two as equivalents.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Chainmail is noticeably lighter than Ironbreaker.
The same difference applies the other way round: Ironbreaker is noticeably darker.
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 Chainmail on the colour wheel
All matches: Ironbreaker equivalents · Chainmail equivalents