ΔE 6.8, close: similar, with a visible difference side by side. Royal Brown is more saturated than Rifle Brown.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Royal Brown is more saturated than Rifle Brown.
The same difference applies the other way round: Rifle Brown is 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 Rifle Brown on the colour wheel See Royal Brown on the colour wheel
All matches: Rifle Brown equivalents · Royal Brown equivalents