Spherical gas atomised 100Cr6 steel powder, processed with the MMS-Scanpac® process to 95% density (agglomeration, followed by conventional pressing, low temperature sintering and re-strike using high velocity adiabatic compaction) has been fully compacted using capsule-free hot isostatic pressing. The material is characterised at different steps of the process and the results are discussed in this paper. Sintering steel powder with high content of carbon requires carbon control at sintering. By continuously measuring the atmosphere at sintering the ingoing gases are adjusted so that carbon control is achieved. Computational work has been made in order to determine how the sintering atmosphere should be adjusted based on the oxygen release and moisture content in the furnace at sintering. KEYWORDS: Capsule free HIP, high velocity compaction, 100Cr6, carbon control.