ΔE 7.2, close: similar, with a visible difference side by side. Obsidian Black is a little darker than Six Shooter.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Obsidian Black is a little darker than Six Shooter.
The same difference applies the other way round: Six Shooter is a little lighter.
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 Six Shooter on the colour wheel See Obsidian Black on the colour wheel
All matches: Six Shooter equivalents · Obsidian Black equivalents