ΔE 10.6, fair: the same colour family, but not a straight swap. Armour Brown is a little lighter than Barrel Grey.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Armour Brown is a little lighter than Barrel Grey.
The same difference applies the other way round: Barrel Grey 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 Barrel Grey on the colour wheel See Armour Brown on the colour wheel
All matches: Barrel Grey equivalents · Armour Brown equivalents