By fibering the duality between the $E_{8}times E_{8}$ heterotic string on $T^{3}$ and M-theory on K3, we study heterotic duals of M-theory compactified on $G_{2}$ orbifolds of the form $T^{7}/mathbb{Z}_{2}^{3}$. While the heterotic compactification space is straightforward, the description of the gauge bundle is subtle, involving the physics of point-like instantons on orbifold singularities. By comparing the gauge groups of the dual theories, we deduce behavior of a half-$G_{2}$ limit, which is the M-theory analog of the stable degeneration limit of F-theory. The heterotic backgrounds exhibit point-like instantons that are localized on pairs of orbifold loci, similar to the gauge-locking phenomenon seen in Hov{r}ava-Witten compactifications. In this way, the geometry of the $G_{2}$ orbifold is translated to bundle data in the heterotic background. While the instanton configuration looks surprising from the perspective of the $E_{8}times E_{8}$ heterotic string, it may be understood as T-dual $text{Spin}(32)/mathbb{Z}_{2}$ instantons along with winding shifts originating in a dual Type I compactification.
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