A fuze malfunction, the second ever in the model’s service history, likely caused a M795 155mm artillery round to explode early in a live-fire demonstration at Camp Pendleton last fall, raining shrapnel onto a civilian highway, the Marine Corps found.
The Marine Corps released its own internal investigation into the Oct. 18 incident on Friday. The incident last fall saw an artillery shell prematurely detonate over Interstate 5 while Marines carried out a live-fire barrage as part of an amphibious assault demonstration. The event, held as part of celebrations for the Marine Corps’ 250th birthday, was attended by Vice President J.D. Vance and Defense Secretary Pete Hegseth, and caused confusion in the hours leading up to it, prompting a last-minute closure of Interstate 5 near the base.
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The Marine Corps determined the issue was the round’s electronic fuze malfunctioning, although the cause of the malfunction wasn’t clear. Per the report, prepared for the commanding general of I Marine Expeditionary Force, the fuze was “manufactured to a one-in-a-million defect standard.” Six M777 howitzers were set up on Red Beach and crewed by Marines from 2nd Battalion, 11th Marine Regiment, 1st Marine Division. They were set to fire artillery into a training area inside Camp Pendleton, on the other side of the freeway. 120 artillery shells were available for the demonstration, the Marine Corps said, and the rounds were fired over Interstate 5, one of California’s busiest highways and serves as the main route between San Diego and Los Angeles; Camp Pendleton sits between the two cities. An Amtrak train line also runs parallel to the freeway by the base.
Investigators couldn’t determine what caused the malfunction, but said that the howitzers’ proximity to one another might have contributed. The six guns fired were closely packed together, placed in a space 165 yards by 165 yards, with two howitzers only 14 feet apart. The report said that “several career artillery officers note they have never seen howitzers placed this close together but also acknowledged that there was no restrictive minimum distance of Gun placement in relation to administrative artillery live fire.” Additionally, the “potential presence of anomalous electromagnetic energy in the vicinity” of the artillery pieces might have played a role.
“The M767A1 fuze is extremely reliable, with only one malfunction in its service history,” the report said. That incident happened at Fort Drum in 2017 when the same fuze, mounted to a 105mm M119A3 round, exploded early after hitting something mid-flight.
Experts, including engineers at the Naval Surface Warfare Center, Corona, examined the evidence from the events leading up to the incident. The shell detonated 453 meters above the highway. Shrapnel, including a two-inch-long piece, fell to the ground, hitting a California Highway Patrol car and motorcycle. No one was injured. The two vehicles hit by the raining shrapnel happened to be assigned to Vance’s security detail; Vance himself was not nearby, instead at the stage where the event’s speakers were at.
The report also noted that President Donald Trump was initially intended to attend the amphibious landing demonstration, which would have necessitated the closure of the highway by Camp Pendleton. However, Vance, a Marine veteran, went instead, which created a possibility of traffic being allowed to pass through.
The premature detonation was the culmination of a chaotic period, after the Marine Corps initially determined that no closure was needed following its own risk assessment. The California government decided, after back and forth with the military and federal government, to close 17 miles of the freeway near the base four several hours, out of safety concerns. Those included the direct risk of the artillery and potential startling of drivers the sound of the howitzers could cause. In the hours ahead of the celebration, electronic signs set up along the highway dozens of miles from the base warned “Live weapons over freeway” as they approached Camp Pendleton.
It was later revealed that Marines fired 30 155mm artillery rounds over Interstate 5 the day prior during a rehearsal, while the highway was still open and cars passed under the arc of the munitions. In the fall, California Highway Patrol said that the Marine Corps did not specify the rehearsal would include live artillery rounds being fired, although the Marine Corps claimed that was announced to California officials.
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