ΔE 10.9, fair: the same colour family, but not a straight swap. Gun Metal is noticeably darker than Iron Hands Steel.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Gun Metal is noticeably darker than Iron Hands Steel.
The same difference applies the other way round: Iron Hands Steel 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.
See Iron Hands Steel on the colour wheel See Gun Metal on the colour wheel
All matches: Iron Hands Steel equivalents · Gun Metal equivalents