This research article uses Magnetic Resonance Velocimetry (MRV), a novel approach, to map the three-dimensional argon gas flow within a commercial metal additive manufacturing (PBF-LB/M) machine's build chamber for the first time. A scaled model of the EOS M290 system was employed to conduct MRV measurements, revealing complex flow patterns including jets, recirculation zones, and separation regions. The study correlates these flow characteristics with melt pool depths resulting from laser scans on titanium plates, demonstrating a direct link between gas flow quality and part quality. The findings highlight the impact of inadequate gas flow on laser power delivery and suggest potential improvements to build chamber design to achieve more uniform flow. An additional vent was implemented to demonstrate that improving problematic flow regions increases melt pool depth.