ΔE 17.2, loose: different enough that you should pick on purpose. Natural Steel is noticeably darker, more saturated than Gun Metal.
✓ AMMO ATOM user guide chart lists these two as equivalents.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Natural Steel is noticeably darker, more saturated than Gun Metal.
The same difference applies the other way round: Gun Metal is noticeably lighter, 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 Gun Metal on the colour wheel See Natural Steel on the colour wheel
All matches: Gun Metal equivalents · Natural Steel equivalents