REBCO coated conductors have a strong potential for high-field magnet applications. The REBCO technology, however, is still in its infancy for accelerator magnet applications. As part of the U.S. Magnet Development Program, we developed a six-layer canted cos θ dipole magnet, C3a, using CORC wires developed by Advanced Conductor Technologies LLC. All the layers were wound using a semiautomated winding machine. Three layers of the magnet used CORC wires containing the SuperPower “AP” REBCO tapes and the remaining layers used the wires containing the “HM” tapes. At 77 K, both kinds of CORC wires showed 5% to 10% degradation, after bending to a minimum bend radius of 30 or 35 mm, with respect to the self-field critical current measured before winding. At 4.2 K, the magnet reached 9.5 kA at a ramp rate of 9 A s-1 and generated a dipole field of 1.4 T. The critical current of one layer degraded by 4% after a current transient up to 10.5 kA ramped in an averaged rate of 175 kA s-1 or 20 T s-1. We confirmed the HM CORC wire can carry a higher current than the AP CORC wire at 4.2 K. The test results of the C3a magnet showed that the fabrication and assembly procedure can be used for the upcoming full-scale C3 magnet.