NSWCDD-PN-18-00119 - DISTRIBUTION A. Approved for public release: distribution unlimited 1
Sheet-metal Ammunition Packing Tray for Mitigation of Secondary Cook-off of
Medium-caliber Ammunition
Presented by
Greg Little, J.P. Shebalin, Jim Fetsko, Joe Silber
Naval Surface Warfare Center Dahlgren Division, Dahlgren, Virginia
Email: greg.little@navy.mil
Phone: 540-653-0187
And
Jeb Brough
Matsys, Inc., Sterling, VA
Abstract
Bullet Impact (BI) and Fragment Impact (FI) Insensitive Munitions (IM) tests against
unlinked, medium-caliber ammunition packaged in ammunition cans with high-density
polyethylene (HDPE) packing trays have demonstrated a secondary hazard distinct from the
rounds’ initial reaction to impact. Specifically, the HDPE trays display a tendency to catch fire as
a result of the impact and initial reaction of the ammunition. This fire begins a sustained series
of secondary cook-offs of projectiles and cartridge cases that lasts until either the fire burns out
or the contents of the ammunition can have reacted or been ejected due to secondary reactions.
This hazard has been witnessed in two types of 25mm ammunition, with two more due
for demonstration testing in 2018. Any munitions packaged in similar trays may be vulnerable to
this phenomenon due to the high energy density of the HDPE and its flammability properties.
Secondary reactions often continue long after the initial impact with no obvious visual indication
that combustion is taking place until a reaction occurs.
Replacement of these trays with a nonflammable alternative would mitigate this safety
hazard. Preliminary testing of prototype sheet-metal ammunition packing trays has
demonstrated favorable results in this regard without degrading the initial IM response.
Currently, design refinements are underway to improve manufacturability of these trays. Once
these refinements are complete, the trays are expected to meet all necessary packaging
requirements (cost, weight, performance) while mitigating the secondary cook-off hazard.
Background
Prior BI and FI testing conducted on containerized, unlinked PGU-47/U Armor-piercing
High-explosive (APEX) 25mm ammunition (developed and tested by Nammo) revealed an
unexpected hazard—the ignition and slow burn of the HDPE packaging trays, resulting in a
series of cook-off reactions, often occurring after a significant delay and continuing for many
minutes afterward (the reaction furthest in time occurred 42 minutes after initial impact). Given
the ubiquity of the HDPE trays in packaging unlinked, medium-caliber ammunition, the similarity
of energetics across ammo types, and the long service life of commonly used medium caliber
