ΔE 6.1, close: similar, with a visible difference side by side. Rifle Brown is a little darker, cooler than Burnt Umber.
Usually, if you are not matching paint already on the model. Close match (ΔE 6). Rifle Brown is a little darker, cooler than Burnt Umber.
The same difference applies the other way round: Burnt Umber is a little lighter, warmer.
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 Burnt Umber on the colour wheel See Rifle Brown on the colour wheel
All matches: Burnt Umber equivalents · Rifle Brown equivalents