Second Careers for Old Bombs: Repurposed Stock Ordnance as Drone Payloads

The cheapest drone munition is the one that already exists. Mortar bombs, hand grenades, and legacy rocket-propelled grenade rounds sit in storage on a scale measured in the tens of millions across the former Soviet space alone, with parallel stocks across NATO's legacy inventories and the wider world's. Demilitarizing them costs money — disposal contracts, surveillance of aging stocks, the liability of holding them at all. Drone delivery offered a second career, and both sides of the Ukraine war took it at scale. The result is a munitions economy in which the payload layer is substantially a repurposing industry, and in which stockpiles written off for a generation have re-entered the order of battle.

The repurposed menu is now standardized enough to name. Eighty-two and 120-millimeter mortar bombs are the reference payloads for heavy bomber drones; hand grenades and 30- and 40-millimeter grenade-launcher rounds serve small drop drones; RPG-class rounds provide the anti-armor warhead for FPVs. The pattern is not unique to Ukraine — repurposed ordnance appeared under drones in Syria, Iraq, and Nagorno-Karabakh earlier — but the current war industrialized it. Conversion moved from unit workshops toward organized production, and employment moved from improvisation to doctrine, with load tables, training syllabi, and stock accounting built around items originally issued for a mortar tube or a human arm.

Adaptation is real engineering, and this desk describes it strictly at the doctrine level. Stock ordnance was designed for a specific employment: mortar fuzing expects launch acceleration and a steep terminal trajectory; grenade mechanisms expect a thrower and a timed sequence; RPG rounds expect a recoilless launch. Drone employment changes the loads, the release geometry, and the initiation conditions, and adaptation means reconciling each item's existing safety-and-arming logic with a delivery mode its designers never certified. Two paths exist: accept the stock behavior and its reliability limits, or modify the item — which moves the activity from logistics into ammunition engineering, with the certification burden that implies. The frontline practice ran ahead of the paperwork on both sides, and the accident statistics were the invoice.

Safety certification is where doctrine meets liability. Storage, transport, and handling regulations for stock ordnance assume the issued configuration; a modified item is, in legal terms, a new munition. States have responded along a spectrum: tacit acceptance at unit level early in the war, then formalized conversion programs with approved designs, inspection regimes, and qualified personnel. The direction of travel is unambiguous. Repurposing is being absorbed into the formal ammunition system because accident rates and dud rates made the informal system too expensive to tolerate, and because ministries discovered that a practice they could not stop was better certified than ignored.