Matt Black vs Battlefield Brown

How close are they?

ΔE 16.1, loose: different enough that you should pick on purpose. Battlefield Brown is noticeably lighter, more saturated than Matt Black.

Can I use Battlefield Brown instead of Matt Black?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Battlefield Brown is noticeably lighter, more saturated than Matt Black.

Can I use Matt Black instead of Battlefield Brown?

The same difference applies the other way round: Matt Black is noticeably darker, 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.