Three grades of HMX samples, coarse (A), coarse with a small amount of fines (B), and ultra-fine (F), were tested for impact sensitivity by ERL drop hammer. The Type 12A test used sandpapers of three different compositions, 120-, 180-grit Si/C and 180-grit garnet. Reaction was accounted for by operator observation and microphone. The results showed different sensitivity for each of the HMX types. The F-HMX was the smallest in average particle size and was the least sensitive to impact. The A-HMX was the next most stable and the B-HMX was the most sensitive to impact. The spent samples from the drop hammer testing of B-HMX and F-HMX were further evaluated with optical imaging. Conditions were selected that were near the DH50 values of the specific HMX. Previous literature has cited localized hot spot formation to be the probable cause of non-shock initiated reactions leading to impact sensitivity. This study yielded a plethora of samples exhibiting hot spots for HMX materials, both without and with proximity to grit particles. Hot spots in the proximity of grit particles gave the most dramatic hot spots, but both types of hot spots were exhibited in samples considered reacted and non-reacted. The F-HMX, even though the most stable to impact sensitivity, exhibited the most and best resolved hot spots of all the samples and conditions. Foreign objects were also observed in some of the samples. Previous work has shown metal particles coming from wear of the anvils used in the drop hammer experiment can also form hot spots. However, none of the samples here with metal particles exhibited, in proximity, hot spot formation.