3D Metal Printing

Radical Defense M249FVS: Laser Sintering Meets Lewis Gun
Forgotten Weapons

Ian McCollum gives us a real world example of 3D Metal Printing as opposed to people making toys and geegaws just to show off what their 3D printer can do:

One of the problems with using suppressors on machine guns is that suppressors or generally much more susceptible to heat buildup than the guns themselves. In 2019, US SOCOM put out a request for a suppressor that could handle a 600 round belt dump on an M240 machine gun. Radical Defense responded by developing a suppressor specifically designed for use with automatic fir, both in its materials and its mechanical design.

Mechanically, they took the concept of the Lewis Gun’s forced-air cooling and integrated it into their suppressor. The outside of the baffle stack is surrounded by a series of hollow channels running the length of the can. Muzzle blast from firing pulls cool outside air through these channels from back to front, cooling the unit. Interestingly, once the can hits about 450 degrees F, the temperature differential between inside and outside will actually generate this forced-air effect without any firing – dramatically increasing the can’s rate of cool-down. In testing, they found that a 600-round burst will heat the can (a 7.62mm version on an M240, specifically) up to 1565F, but 10 minutes later it will have dropped to 484F. After an additional 20 minutes, the can was down to ambient temperature.

From a materials standpoint, a very heat-resistant alloy was chosen. It is more than 50% nickel, with a significant portion of cobalt. This allows the can to withstand those extremely high temperatures generated by sustained fire. Manufacturing is done via laser sintering, allowing all the complex geometry of the suppressor baffles and cooling channels to be formed without the insanely complex machining fixtures and/or welding that would be required by traditional manufacturing processes. This is a very cool example of 3D printing technology being used to produce geometries that would be unfeasible just a few years ago.

The original design was in 7.62mm, for the M240. What I have in this video is the 5.56mm version, just the same thing scaled down for the M249. A version for the 12.7mm M2 is also in the works. The downsides to its capabilities are significant cost and weight (this 5.56mm version weighs 2lb 7oz). However, Radical is already developing a significantly lightened second generation of both sizes.

Thanks to Radical Defense for the loan of this example for filming! I saw them at SHOT Show and was really taken by the combination of century-old design concepts and totally cutting-edge manufacturing processes.

SOCOM is Special Operations Command

SHOT Show is the Shooting, Hunting and Outdoor Trade Show

Here's a primer on how this 3D Metal Printing works:

How it Works: Direct Metal Laser Sintering (DMLS)
Stratasys Direct Manufacturing
3D Printing is slow, it will take hours and perhaps even days to print large part. On the other hand, all you need is the big 3D printer. No machine tools, no welding, cutting or forging required. The alloy they are using can withstand very high temperatures. 1500 degrees Fahrenheit is seriously hot. And it's expensive. On the other hand, I'm not sure you could even build this device using any other technique.