  We analyze three Chandra observations, with a combined exposure time of 99
ks, of the Galactic supernova remnant RCW 103, a young supernova remnant,
previously with no clear detection of metal-rich ejecta. Based on our imaging
and spectral analyses of these deep Chandra data, we find evidence for
metal-rich ejecta emission scattered throughout the remnant. X-ray emission
from the shocked ejecta is generally weak, and the shocked circumstellar medium
(CSM) is a largely dominant component across the entire remnant. The CSM
component shows abundances of ~0.5 solar, while Ne, Mg, Si, S, and Fe
abundances of the ejecta are up to a few times solar. Comparison of these
ejecta abundances with yields from supernova nucleosynthesis models suggests,
together with the existence of a central neutron star, a progenitor mass of
~18-20 M$_\odot$, though the Fe/Si ratios are larger than predicted. The
shocked CSM emission suggests a progenitor with high mass-loss rate and
subsolar metallicity.
