ISC Defence Intelligence
Corroded 25mm HEI Round Recovered at Palm Springs Airport: EOD Render-Safe and Ordnance Accountability Gaps
A “found round” kept as a souvenir is routinely dismissed as a harmless curiosity — but the corroded 25mm High Explosive Incendiary round discovered in checked luggage at Palm Springs required full EOD X-ray assessment because corrosion had eliminated every external indicator of its live status.
Technical Summary
On 30 March 2026 at approximately 12:05 local time, Transportation Security Administration (TSA) personnel at Palm Springs International Airport (PSP) discovered a corroded 25mm round in the checked luggage of a US Marine during routine X-ray screening. The round was extensively corroded with no visible identifying markings, preventing initial visual classification by TSA staff.
The Riverside County Explosive Ordnance Disposal (EOD) Unit responded and conducted X-ray assessment of the item, confirming that it was a live 25mm High Explosive Incendiary (HEI) round with the fuze, explosive fill, and incendiary composition intact. The round is assessed as an M792 HEI-T (High Explosive Incendiary with Tracer) or similar variant, fired from the M242 Bushmaster 25mm chain gun mounted on the LAV-25 and other armoured fighting vehicles in US Marine Corps service.
The Marine stated he had found the round in a field approximately one year prior and retained it, believing it to be inert. Corrosion had obscured all external lot markings, colour coding (blue body for practice, olive drab for HE), and fuze condition indicators. Only X-ray examination could confirm the internal explosive content. The round was subsequently transported to a remote desert location and destroyed by controlled high-order detonation.
M792 25mm HEI-T Round — Assessed Technical Parameters
Designation: M792 High Explosive Incendiary with Tracer (HEI-T)
Calibre: 25 × 137 mm NATO
Weapon platform: M242 Bushmaster chain gun (LAV-25, Bradley IFV, Stryker ICVD)
Projectile mass: ~185 g (complete round ~500 g)
Explosive fill: ~26 g of A-5 (RDX/wax 99/1) or PBXN-5
Incendiary: Zirconium-based incendiary composition in nose
Fuze: M758 point-detonating base-detonating (PDBD) fuze; arms on setback acceleration
Arming: Setback-armed during firing; found rounds may be unarmed but explosive fill remains sensitive
Hazard Division: HD 1.2 E (fragment-producing; non-mass-detonating)
Analysis of Effects
Explosive Hazard Assessment
The M792 HEI-T projectile contains approximately 26 g of high-explosive fill, producing an estimated NEQ of 0.026 kg TNT equivalent. High-order detonation generates a lethal radius (LR) of approximately 5 metres for unprotected personnel and a casualty radius (CR) of approximately 15 metres from the combined blast, fragmentation, and incendiary effects. The projectile body fragments into approximately 40–60 natural fragmentation pieces at velocities of approximately 1,200 m/s.
The zirconium-based incendiary composition in the nose burns at temperatures exceeding 2,000 °C, presenting an additional thermal hazard. In an enclosed environment such as an aircraft baggage hold, the combined blast overpressure, fragmentation, and incendiary effects of a 25mm HEI detonation could compromise the pressure vessel integrity of the fuselage, with potentially catastrophic consequences for aircraft structural integrity at altitude.
Corrosion and Stability Considerations
Extensive corrosion of the round’s exterior raises specific stability concerns. Corrosion of the fuze body may compromise the mechanical safety features that prevent inadvertent initiation. The M758 fuze relies on a setback-activated slider mechanism — if corrosion has degraded the slider retention, the fuze sensitivity to impact and vibration may be elevated above its design threshold. Corrosion products (primarily iron oxide) in contact with explosive compositions can create sensitised interfaces, reducing the stimulus threshold for unintended initiation.
The corroded condition also eliminated all external identifying features, making visual identification impossible. This is precisely the scenario where EOD X-ray capability is essential: the internal explosive column, fuze mechanism, and incendiary fill are only visible through radiographic assessment. TSA personnel correctly escalated to EOD rather than attempting manual assessment.
Personnel and Safety Considerations
The Riverside County EOD response followed established protocols for suspected explosive items in civilian aviation environments. X-ray assessment confirmed the item as live, and the decision to transport to a remote location for controlled demolition is consistent with ALARP principles — no requirement existed for in-situ render-safe given the ability to move the item safely.
For Ammunition Technical (AT) and EOD personnel, this incident reinforces a recurring pattern: military ordnance found in training areas is frequently retained by service members who incorrectly assess items as inert based on external appearance. Corrosion obscures colour-coding systems (olive drab for HE, blue for practice, yellow band for HE fill) that are the primary visual identification method for 25mm ammunition natures. Without X-ray or technical reference data, no visual assessment of a corroded round can confirm its inert status.
Transport of military explosive articles by air is prohibited under the International Air Transport Association (IATA) Dangerous Goods Regulations unless specifically authorised under a military exemption. The 25mm HEI-T round is classified as UN 0328 (Cartridges for weapons, inert projectile) in its practice variant, but as UN 0006 (Cartridges for weapons, with bursting charge) in its HE configuration — a Hazard Division 1.1 E item prohibited from civilian air transport without exception.
Data Gaps
DATA GAP: Exact round variant — Whether the item is an M792 HEI-T, M793 TP-T (Target Practice with Tracer), or another 25mm variant cannot be confirmed from press reporting alone. Only the EOD X-ray assessment can distinguish between HEI and TP rounds when external markings are absent. Press reports confirm EOD assessed it as “live and operational.”
DATA GAP: Origin and lot — The field location where the round was found, the unit that may have expended it, and the lot number are all unknown. This information would be relevant for determining whether a wider contamination or accountability issue exists at the training area in question.
DATA GAP: Fuze condition — Whether the M758 fuze was in the armed or safe condition was not reported. For a found round (unfired), the fuze should be in the safe position, but corrosion degradation of the slider retention mechanism cannot be confirmed without disassembly or X-ray.
Corrections & updates welcome. If you hold open-source data that refines or corrects any parameter in this article, please contact [email protected] citing the specific claim and your source. Verified corrections will be incorporated and credited in the revision history.
Sources & References
- [1] Palm Springs Today, “Marine Arrested at Palm Springs Airport with Live Explosive Round in Luggage,” 31 March 2026. [C/2]
- [2] US Army, TM 43-0001-27, Army Ammunition Data Sheets: Small Calibre Ammunition. [A/1]
- [3] IATA Dangerous Goods Regulations, 67th Edition, 2026. [A/1]
- [4] UN Recommendations on the Transport of Dangerous Goods, Model Regulations, Rev. 23. [A/1]
- [5] DSA 03.OME, Defence OME Safety and Environmental Management, UK Ministry of Defence. [A/1]