  We present results from two Chandra/ACIS observations of the so-called Vela
``Bullet D'' region on the eastern limb of the Vela supernova remnant. The
Bullet D region is a bright X-ray feature, identified by Aschenbach et al.
(1995) from the ROSAT All-Sky Survey, which protrudes beyond the blast wave on
the eastern side of the remnant. It has been suggested that this feature is a
fragment of supernova ejecta which is just now pushing beyond the position of
the main blast wave. An alternate explanation is that the feature is a
``break-out'' of the shock in which inhomogeneities in the ambient medium cause
the shock to be non-spherical. The Chandra image shows a fragmented,
filamentary morphology within this region. The Chandra spectra show strong
emission lines of O, Ne, and Mg. Equilibrium ionization models indicate that
the O and Ne abundances are significantly enhanced compared to solar values.
However, non-equilibrium ionization models can fit the data with solar O
abundances and Ne abundances enhanced by only a factor of two. The Chandra data
are more consistent with the shock breakout hypothesis, although they cannot
exclude the fragment of ejecta hypothesis.
