  We present a second epoch of {\it Chandra} observations of the Type Ia LMC
SNR 0509-68.7 (N103B) obtained in 2017. When combined with the earlier
observations from 1999, we have a 17.4-year baseline with which we can search
for evidence of the remnant's expansion. Although the lack of strong point
source detections makes absolute image alignment at the necessary accuracy
impossible, we can measure the change in the diameter and the area of the
remnant, and find that it has expanded by an average velocity of 4170 (2860,
5450) km s$^{-1}$. This supports the picture of this being a young remnant;
this expansion velocity corresponds to an undecelerated age of 850 yr, making
the real age somewhat younger, consistent with results from light echo studies.
Previous infrared observations have revealed high densities in the western half
of the remnant, likely from circumstellar material, so it is likely that the
real expansion velocity is lower on that side of the remnant and higher on the
eastern side. A similar scenario is seen in Kepler's SNR. N103B joins the rare
class of Magellanic Cloud SNRs with measured proper motions.
