  MCG-5-23-16 was targeted in early 2015 with a half mega-seconds observing
campaign using NuSTAR. Here we present the spectral analysis of these datasets
along with an earlier observation and study the relativistic reflection and the
primary coronal source. The data show strong reflection features in the form of
both narrow and broad iron lines plus a Compton reflection hump. A cutoff
energy is significantly detected in all exposures. The shape of the reflection
spectrum does not change in the two years spanned by the observations,
suggesting a stable geometry. A strong positive correlation is found between
the cutoff energy and both the hard X-ray flux and spectral index. The
measurements imply that the coronal plasma is not at the runaway
electron-positron pair limit, and instead contains mostly electrons. The
observed variability in the coronal properties is driven by a variable optical
depth. A constant heating to cooling ratio is measured implying that there is a
feedback mechanism in which a significant fraction of the photons cooling the
corona are due to reprocessed hard X-rays.
