Many extensions to the Standard Model predict the existence of new, massive, long-lived particles. Such heavy particles produced in proton-proton collisions at a center-of-mass energy of 13 TeV are expected to move significantly slower than the speed of light. A slow-moving charged particle will lose more energy via ionization as it traverses detector material than a particle moving near the speed of light. This property can be used to identify slow-moving charged long-lived particles, which should appear in a detector as a trajectory with high momentum and anomalously large ionization energy loss. The first search for heavy, long-lived, charged particles using ionization energy loss in the full ATLAS Run 2 dataset observed an excess with a global significance of 3.3σ at high mass. We discuss these results and present a followup search for slow-moving particles in 140.1 fb-1 of ATLAS Run 2 data. This new search expands the analysis strategy by incorporating a second measure of particle speed, time-of-flight measurements, to significantly reduce background and improve sensitivity to heavy, charged, long-lived particles. Results are interpreted in terms of supersymmetric models that predict long-lived gluinos and sleptons.