This is RAMBO, but it has nothing to do with the protagonist from the 80s movie franchise adaption of David Morrell’s 1972 novel, First Blood. This RAMBO here is not a person; it is a weapon – a grenade launcher to be exact. What makes RAMBO so special is, it is grenade launcher made almost exclusively from addicted manufacturing, AKA 3D printing, and it actually fires, wait for it… 3D-printed munition. And the name there? It actually stands for Rapid Additively Manufactured Ballistics Ordnance. Pretty sure it is not a nod to the fictional hero.
Developed by researchers at the U.S. Army Armament Research, Development and Engineering Center (ARDEC), RAMBO is a “technology demonstrator” to determine if 3D printing “is mature enough to build an entire weapon system and the materials’ properties robust enough to create a properly functioning armament.” Obviously, not all of the 50 individual components of this modified version of the older 40 mm grenade launcher M203A1 were 3D-printed.
Parts like fasteners and springs that have the critical task of holding everything together were not – so were the barrel and receiver, as well as trigger and firing pin. Barrel and receiver were fabricated in aluminum using a process known as direct metal laser sintering (DMLS) while trigger and firing pin were printed in 4340 alloy steel. DMLS, btw, is kind of like 3D printing, except that high-powered precision lasers were used to heat particles of powder to below their melting point, thus essentially welding the fine metal powder layer by layer until a finished object was formed.
Of course, the entire process was not as simple as print-and-assemble; it has a few post-printing processes too, like in the case of the aluminum receiver and barrel, machining and tumbling were required and in the case of AM components, they had to be snipped from the build plate, the support material removed and whatnot. All told, 5 hours of post process was required for the barrel and receiver alone which itself took around 70 hours to print. The grenade launcher itself took 35 hours to print on a single build plate. The time and cost involved are significantly lesser over conventional methods which would take months and costs tens of thousands of dollars.
And then there is, of course, the 3D printed ammunition, the 40 mm M781 training round. The particular round was chosen because of its simplicity and non-involvement of any form of energetics, explosives, propellants or otherwise. Here are what you need to know about the M781:
“The M781 consists of four main parts: the windshield, the projectile body, the cartridge case and a .38-caliber cartridge case. The windshield and cartridge case are traditionally made by injection molding glass-filled nylon. Using multiple AM systems at multiple locations helped emphasize manufacturing readiness and the Army’s capability to design, fabricate, integrate and test components while meeting tolerances, requirements and design rules. ARL and ECBC used selective laser sintering and other AM processes to print glass-filled nylon cartridge cases and windshields for the rounds.”
The .38-caliber cartridge case was the only component not printed. It was pressed from purchased zinc material. Anywho, RAMBO develop is considered complete and a success when both AM-printed products were live-fire tested back in October 12, 2016, at the Armament Technology Facility at Picatinny Arsenal, NJ. That said, given the report by U.S. Army was two-year-old, things may have progressed significantly since.
With this development, along with other 3D printing advancements, a future like real-time strategy game (RTS) where military factions had their building and weapon manufacturing plants within the reach of battlefield is not far away. You can learn more about RAMBO and the munition in the two-year-old official video embedded below.
Images: U.S. Army.
Source: The National Interest.