ΔE 3.8, very close: most people won’t see a difference side by side. Matt Black Primer is a little lighter than Black. They are different kinds of paint: AK Interactive Black is an opaque base/layer paint and Army Painter Matt Black Primer is a technical paint or medium, so they won’t behave the same on the model even where the colour is close.
Yes, for most jobs. Very close match (ΔE 4). Matt Black Primer is a little lighter than Black. They are different kinds of paint.
The same difference applies the other way round: Black is a little darker.
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 Black on the colour wheel See Matt Black Primer on the colour wheel
All matches: Black equivalents · Matt Black Primer equivalents