I know where that is! of course Maganru does to
I can see it from here.
I am of the same family of Maganru and we always spelled and said it as Achnaduie but the family in Macharioch always pronounced it and I suppose, spelled it AchadAhdubh ....... Aucha da dooie.
But, there is no doubt it is the same place.
In the fairly recent past the roof was still on and within the last 30 years a high gable end could still be seen but now the ruins are low.
The Gillies family mentioned by Maganru is that of famous Campbeltown author and ferry captain Freddy Gillies and he has often told me his stories from there expressed an interest in the place . I will take him there some day.
AND, as it happens, I am going a walk with 2 of Maganru's cousins tonight very close to Achadhdubh/Achnaduie and will take my camera.