  The Martensitic transformation (MT) in A15 binary-alloy superconductor V_3Si,
though studied extensively, has not yet been conclusively linked with a
transition to superconductivity. Previous NMR studies have mainly been on
powder samples and with little emphasis on temperature dependence during the
transformation. Here we study a high-quality single crystal, where quadrupolar
splitting of NMR spectra for ^51V allowed us to distinguish between spectra
from transverse chains of V as a function of temperature. Our data revealed
that (1) the MT is not abrupt, but rather there is a microscopic coexistence of
pre-transformed cubic phase and transformed tetragonal phase over a few K below
and above Tm, while (2) no pre-transformed phase can be found at Tc, and (3)
the Martensitic lengthening of one axis occurs predominantly in a plane
perpendicular to the crystal growth axis, as twinned domains.
