  The present paper deals with mirror symmetry aspects of compact ``barely''
$G_2$ manifolds, that is, $G_2$ manifolds of the form (CY$\times
S^1)/\mathbb{Z}_2$. We propose that the mirror of any barely $G_2$ manifold is
another barely one and which is constructed as a fibration of the \emph{mirror}
of the CY base. Also, we describe the Joyce manifolds of the first kind as
``barely'' and we show that the underlying CY of all the family is self-mirror
with $h^{1,1}=h^{2,1}=19$. We thus propose that the mirror of a Joyce space of
the first kind will be another Joyce space of the first kind.We also suggest
that this self-mirror CY family is dual to K3$\times S^1$ in the
heterotic/M-theory sense, and that arise as a particular case of the
Borcea-Voisin construction. As a spin-off we conclude from this analysis that
no 5-brane instantons are present in compactifications of eleven dimensional
supergravity over Joyce manifolds of the first kind.
