us-army-logoA couple years ago, a program responsible for training workers on weapon removal, like land mines and grenades, utilized 3D printing kits as teaching aids. Around the same time, some clever kids developed a 3D printed stink grenade. But now, the US Army is introducing a 3D printed grenade launcher, complete with 3D printed grenades, that could revolutionize how soldiers are equipped for warfare. Aptly, the weapon was named RAMBO, which stands for Rapid Additively Manufactured Ballistics Ordnance, and is a modified version of the army’s existing M203 underslung grenade launcher, which can be used for firearms like the M4A1 carbine and the M16. A major difference is that all of RAMBO’s parts, except the springs and fasteners, were produced through additive manufacturing.

The additive-manufactured RAMBO system includes an NSRDEC-designed standalone kit with printed adjustable buttstock, mounts, grips and other modifications—modifications made possible by the quick turnaround time afforded by 3D printing. (U.S. Army photo by Sunny Burns, ARDEC) (Photo Credit: U.S. Army)

The additively-manufactured RAMBO system includes an NSRDEC-designed standalone kit with printed adjustable buttstock, mounts, grips and other modifications—modifications made possible by the quick turnaround time afforded by 3D printing.

According to Military Factory, the M203 has been around since the late 1960s, and is a single-shot, reusable 40 mm grenade launcher. It’s attached underneath the barrel of an assault rifle or other carbine-type weapon, and is designed to be used without any major modifications to the base weapon. The breech-loaded, 3D printed RAMBO grenade launcher is made up of 50 separate parts, most of which were additively manufactured. The receiver and the barrel were 3D printed with aluminum using a DMLS process, and the firing pin and trigger were manufactured using ultra-tough 4340 alloy steel.

M203 [Image: Machine Factory]

M203 [Image: Machine Factory]

The production of RAMBO was a six-month collaborative effort by the US Army Manufacturing Technology (ManTech), the US Army Research, Development and Engineering Command (RDECOM), and national 3D printing accelerator America Makes. The goal was not to determine if 3D printing could make the grenade launcher and munitions production process less expensive, or the items themselves more lightweight, but instead to determine if the technology could actually build a whole weapon system, and if the material properties were hardy enough to produces armaments that functioned the way the military needs them to.

AM-printed rounds, like this one, were fired from the 3D-printed launcher at indoor ranges and outdoor facilities. 15 test shots did not produce any signs of degradation, and the rounds' muzzle velocities were within 5% of the velocities achieved by standard launchers.

AM-printed rounds, like this one, were fired from the 3D-printed launcher at indoor ranges and outdoor facilities. 15 test shots did not produce any signs of degradation, and the rounds’ muzzle velocities were within 5% of the velocities achieved by standard launchers.

While 3D printing definitely helped RAMBO’s production process, it was a process, in the truest sense of the word. Once the barrel, which was printed vertically, came off the print bed, support materials needed to be removed, and it was tumbled and polished in an abrasive rock bath. The receiver also required some post-processing, and then both parts went through a hard-coat anodizing process, in order to create a hard, abrasion-resistant outer layer on the aluminum’s surface. Both of these parts took about 70 hours to print, with roughly five hours of post-process machining.

ManTech also requested that a grenade be 3D printed, based on the M781 40 mm training round, as it does not require explosive propellants; this has not yet been deemed safe with objects that are 3D printed. Two RDECOM R&D centers – the US Army Research Lab (ARL) and the US Army Edgewood Chemical and Biological Center (ECBC) participated in manufacturing the munition. The M781 is made up of the cartridge case, the projectile body, the windshield, and a .38-caliber cartridge case. SLS, along with other additive manufacturing processes, was used to 3D print glass-filled nylon cartridge cases and windshields, but the projectile body, typically made of zinc, was a different story.

m781-components

These M781 components were 3D-printed during a six-month collaborative effort that involved RDECOM, ManTech and America Makes, the national accelerator for additive manufacturing and 3D printing. They cost tens of thousands of dollars less than identical components created with standard production methods.

3D printing with zinc is not possible within the US Army right now, and this is where the iterative beauty of 3D printing comes in. It was quickly determined that aluminum would not work for this part, so the researchers tried 3D printing the projectile body in steel, and then molded a urethane obturating ring onto it, but the ring caused a problem. Finally, a wax printer and the lost-wax casting process were used to 3D print the projectile body. Once the plaster set around the wax bodies, it was heated up, and the wax melted off. Then, molten zinc was poured into the mold for casting.

There are 50 components in the M203 grenade launcher, and all of the parts except for springs and fasteners were produced with 3D printing. This was a promising first for ARDEC.

There are 50 components in the M203 grenade launcher, and all of the parts except for springs and fasteners were produced with 3D printing. This was a promising first for ARDEC.

Researchers at the US Army Armament Research, Development and Engineering Center (ARDEC) successfully live-fire tested RAMBO a few months ago, firing the first 3D printed grenade from the first 3D printed grenade launcher; in all, RAMBO fired a total of 15 shots before showing any signs of deterioration. The technology, as we know, definitely has major military implications, as weapons could be manufactured and tested within days, instead of months, while also being more lightweight. The 3D printed grenade launcher and components were exhibited at the 2016 Defense Manufacturing Conference, and the live-fire demonstration showed that additive manufacturing “has a potential future in weapon prototype development.”

Army researchers stated that 3D printing technology signifies “a new era of rapidly developed, testable prototypes that would improve products and facilitate faster and more efficient transition from the labs to the field.” The RAMBO system, along with its components and rounds, is currently undergoing more tests, to evaluate failure rates, mechanisms, and reliability. Discuss in the 3D Printed Grenade Launcher forum at 3DPB.com.

[Sources: International Business Times, US Army, Machine Factory / Images: US Army, by Sunny Burns, ARDEC, unless otherwise noted]

 

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