America's lean, mean fighting machine may get a bit more lean in the coming years when it comes to ammunition. The Marine Corps is close to picking up a new polymer ammo for its tried-and-true M2 Browning .50 caliber machine gun to lighten the load for grunts downrange.

The Marine Corps is currently negotiating an indefinite delivery, indefinite quantity contract with Mississippi-based defense contractor MAC LLC to evaluate and test the company's lightweight MK 323 Mod 0 polymer ammo, Marine Corps Systems Command spokesman Manny Pacheco told Task & Purpose.

Following testing and qualification, the Corps plans on conducting limited user evaluation of the MK 323 ammo as part of a service-wide effort “to reduce the weight burden, enhance operational reliability, improve mobility and enhance survivability of the warfighter,” Pacheco said.

Guns photo

MK 323 Mod 1 polymer ammo(MAC LLC/Nammo)

First developed by MAC LLC prior to the company's purchase by Norway-based defense contractor (and current M72 LAW provider) Nammo in 2018, the company claims that adopting polymer ammo could yield reduce a 30 percent weight reduction for infantry Marines downrange.

According to Nammo spokesman David Rolen, a standard ammo can filled with 100 linked MK 323 cartridges is more than 12 pounds lighter than one filled with 100 traditional brass .50 cal BMG cartridges and links, a weight reduction from 34.8 pounds to just 26.6 pounds (or 23 pounds if you swap out the ammo can for a specially-made polymer box).

The benefits of a lighter load don't just extend to the individual warfighter. A cache of 1,500 MK 323 ammo weights 120 pounds less than 1,500 standard brass cartridges, a weight reduction that will allow Marine vehicles to “either loiter longer, travel further, or carry other munitions,” as Rolen put it.

The Corps has been examining emerging technologies in search of lighter ammo since 2016, when the service joined with the Army to stand up the Joint Lightweight Ammunition Integrated Product Team to focus on decreasing the weight of direct-fire ammunition — namely .50 cal BMG and the Army's 7.62mm round — by at least 10 percent.

But while the MK 323's weight-saving capability is its main selling point, Nammo emphasized that polymer ammo has the added benefit of improving the accuracy of precision fires like the Barrett M107 sniper rifle.

According to Rolen, manufacturing brass cartridges involves forming a small brass cup into a casing and then further shaping the malleable brass for a specific caliber. This process involves high pressure and heat treating, both of which produce imperfections that affect the internal and external ballistics of a cartridge and, ultimately, the performance of each round.

By contrast, Rolen said, the molding process behind polymer ammo is significantly more exact than brass case manufacturing, meaning that polymer cases (and the amount of propellant within them) are generally more consistent than brass cases and, therefore, more accurate.

Guns photo

The U.S. Army's Joint Program Executive Office Armaments & Ammunition has been evaluating concepts for new 7.62mm ammunition casings for their weight and operational performance compared with traditional brass ammunition, left.(U.S. Army photo)

What does all this mean for the average Marine? Better accuracy and round-to-round consistency, according to Rolen. When all of your cartridges have nearly the exact same case consistency and propellant load, it means all your bullets will leave your rifle barrel at nearly the exact same velocity, a critical factor for ensuring a long-range hit.

With the Pentagon three years into its broad search for lighter ammo, MAC LLC isn't just pitching polymer to the Marines. Rolen also hopes to partner with U.S. Special Operations Command to produce polymer .338 Norma Magnum cartridges as part of SOCOM's quest for
a new long-range machine gun.

For now, though, it's Marine grunts who can look forward to humping a lighter load downrange. And while polymer ammo may not sounds as bad-ass as, say,
a 500-round ammo backpack, chances are they're a hell of a lot better for your back in the long run.