ΔE 18.7, loose: different enough that you should pick on purpose. Bastion Grey is noticeably darker, much more saturated than Administratum Grey.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Bastion Grey is noticeably darker, much more saturated than Administratum Grey.
The same difference applies the other way round: Administratum Grey is noticeably lighter, much 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 Administratum Grey on the colour wheel See Bastion Grey on the colour wheel
All matches: Administratum Grey equivalents · Bastion Grey equivalents