Explosives and energetics continue to be prominent contaminants on many military installations. This research was undertaken to understand the extent to which microscale (10's of mu m) particles are produced when macroscale residues are weathered by artificial precipitation. Initial experiments, in which artificial rainwater was applied drip-wise to single chunks of Composition B detonation residues from multiple heights, confirmed that microscale particles were produced during precipitation-driven aging, with 30% of the explosive mass collected detected as particulate Composition B (e.g., particles >0.45 mu m in diameter). Follow-on experiments, during which multiple cm-sized residue chunks were subjected to realistic simulated precipitation, demonstrated an initial large pulse of particulate Composition B, followed by sustained production of microscale particles that represented 15-20% of recovered explosives. These findings indicate that the effective footprint of detonation residues likely increases as particulates are produced by the production and spreading of microscale particles across the soil surface. Combined with results published elsewhere that microscale particles can move into porous media to become a distributed source term, these findings point to the need for inclusion of these processes in explosive contaminant fate and transport modeling. (C) 2014 Elsevier B.V. All rights reserved.