Metal binder jetting (MBJ) is a promising additive manufacturing technology, offering advantages including higher printing speed and lower residual stress in printed parts compared to other metal additive manufacturing technologies. However, to attain the full commercial potential of MBJ, there is strong interest from industry to substitute high cost spherical powder with lower cost non-spherical powder, like water atomized powder (WAP). The problem is that the non-sphericity of WAP leads to low powder bed packing fraction (i.e., the quotient of the powder bulk density and the particle density), which in turn increases the porosity and shape distortion of the printed parts. The packing fraction and final quality of MBJ parts printed using WAP could be improved by implementing real-time closed-loop control on the packing density. However, there are no suitable approaches to measure packing fraction in-situ during MBJ to facilitate closed-loop control. This paper addresses this shortcoming by hypothesizing that recoating force in MBJ is a suitable signal for accurately measuring packing density in-situ. To test this hypothesis experimentally, an apparatus consisting of a moving powder bed compacted by a recoater attached to a torque sensor was designed and prototyped. In the experiment, the packing fraction of the powder bed was varied to 15 different levels and the recoating force was measured for each case using the apparatus. The mean recoating force was seen to have an almost linear relationship with the packing fraction (with $R^2$ values of 0.91 and 0.93 for two cases investigated) thus supporting our hypothesis. However, the 95\% confidence intervals for the measurements were observed to be large, indicating the need for further work to improve the precision of the measurements.