Boron rich compounds are attractive materials for armor related applications. Boron suboxide (B6O) is one of the most promising candidates for this purpose, owing to its low density and high hardness. However, sintering of this compound has been challenging over the years. We successfully synthesized boron suboxide and sintered with various sintering aids, in spark plasma sintering (SPS) at different temperatures under 50MPa, in a graphite die, with BN sprayed on all surfaces in contact with the sample. High density pellets around 99% of the theoretical density were obtained. Elastic constants were measured by employing ultrasound technique. Average Vickers hardness was found to be ~30GPa under 1Kg load. X-ray diffraction, scanning electron microscopy, and Raman spectroscopy of the sintered pellets confirmed the existence of boron suboxide in thermodynamic equilibrium with these sintering aids.