ΔE 21.5, loose: different enough that you should pick on purpose. Gunmetal Grey is noticeably lighter, more muted than Canoptek Alloy.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Gunmetal Grey is noticeably lighter, more muted than Canoptek Alloy.
The same difference applies the other way round: Canoptek Alloy is noticeably darker, more saturated.
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 Canoptek Alloy on the colour wheel See Gunmetal Grey on the colour wheel
All matches: Canoptek Alloy equivalents · Gunmetal Grey equivalents