ΔE 21.5, loose: different enough that you should pick on purpose. Ancient Copper is a little darker, much more saturated, warmer than Heirloom Gold.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Ancient Copper is a little darker, much more saturated, warmer than Heirloom Gold.
The same difference applies the other way round: Heirloom Gold is a little lighter, much more muted, cooler.
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 Heirloom Gold on the colour wheel See Ancient Copper on the colour wheel
All matches: Heirloom Gold equivalents · Ancient Copper equivalents