ΔE 33.0, loose: different enough that you should pick on purpose. Primer Black Brown is noticeably darker, more saturated than Astrogranite.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 33). Primer Black Brown is noticeably darker, more saturated than Astrogranite.
The same difference applies the other way round: Astrogranite 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 Astrogranite on the colour wheel See Primer Black Brown on the colour wheel
All matches: Astrogranite equivalents · Primer Black Brown equivalents