U.S. Army replaces WWII-era metal ammo cans with polymer SixPAC, eyes 3D printing

As supply chains grow increasingly fragile, the U.S. Army has introduced what it describes as the first major overhaul of ammunition packaging since World War II. Officials also signaled interest in eventually producing ammunition cases on demand using advanced manufacturing techniques.

SixPAC: A New Polymer Ammunition Container

In late August, the U.S. Army Combat Capabilities Development Command Armaments Center at Picatinny, New Jersey, announced the development of the SixPAC — a polymer ammunition container designed to hold 6.8mm rounds for the service's upcoming Next Generation Squad Weapon. Two SixPAC units fit inside a conventional wire-bound outer packaging.

Development of the lighter, simpler-to-manufacture polymer system has been underway for roughly a decade, according to Picatinny officials. However, they noted that the need for alternative materials has become more urgent in recent years.

Addressing Supply Chain Vulnerabilities

"We've had a lot of challenges with metal ammo containers lately, because we just have a limited number of U.S. suppliers," said Jason Runell, senior scientific technical manager for packaging at Picatinny. He added that the Army had traditionally sourced from two manufacturers and at one point was down to just one.

"You need an entire facility just to make one ammo can with all the presses and the dies and the welding equipment and everything. So it's a high barrier to entry and a limited supply."

By contrast, officials estimate that more than 800 U.S.-based injection molders can produce the new packs, eliminating a major production bottleneck.

Weight Reduction and Soldier Feedback

At approximately 2.8 pounds, the new polymer packs are about half the weight of their predecessors. In a release announcing the new packs, Army officials cited feedback from soldiers who tested them during evaluation events between 2024 and 2025.

"Several service members pointed out that when aboard watercraft or aircraft, 'every ounce counts' and that the new system will allow them to carry more ammunition," the release stated.

Future Expansion to Legacy Calibers

Officials hope to eventually make the polymer cases standard for all legacy small-arms calibers, including 5.56mm and .50 caliber. They noted that 7.62mm ammunition is typically packaged in a smaller case than the standard M2A2 ammo can and would require additional engineering.

"We're really using 6.8mm as our proof of concept to scale up and make sure that getting this new technology out into the hands of users is going to be well received," said Karl Weiss, supervisor for small and medium caliber ammunition and weapons packaging. "And there'll be a reverse demand to push this back … and the SixPAC, which could replace the M2A2."

Rigorous Testing Ahead

Before widespread adoption, the polymer shell must undergo additional ruggedness testing to finalize the design.

Ed Lucas, design lead for the polymer ammunition container, said multiple SixPAC variants will be tested in operational environments, including exposure to temperature extremes ranging from 160°F to -65°F.

"We have various tests that simulate all of the different things that this will go through, whether it be being thrown off the back of a tactical vehicle. There's even testing for if it's dropped off a [ship]," Lucas said. "There's a test that quantifies everything that this is going to have to do, and we've been very carefully looking at all those … to see if we can get the most efficient pack we can in soldiers' hands."

User testing will also continue. Past evaluations took place at:

• Fort Benning, Georgia
• Fort Campbell, Kentucky
• Fort Drum, New York
• An ammunition supply point in Germany

Additional user tests are expected at Fort Campbell.

3D Printing as a Stopgap Solution

As the Army advances its 3D printing capabilities, Picatinny officials are exploring the technology for emergency ammo can production. Runell said research on 3D-printed ammunition containers is scheduled to begin next fiscal year.

"We want to first look into 3D printing for the purposes of addressing production surge. So, if we do have production surges where our ammunition packaging manufacturers can't keep up with demand, there may be a way to insert 3D-printed containers as a stopgap solution," he said.