Michigan-based Sintercore is billing its Auxetik (pronounced Aug-ZETIK) as the first commercial 3D printed firearm muzzle brake. Made of Inconel alloy using a laser additive manufacturing process, the Auxetik is designed to tame the recoil and muzzle rise of AR-15 pistols chambered for .223 caliber (5.56x45mm) NATO rounds.
The AR-15 is the semi-automatic civilian version of the military M-16, which is used by over 80 countries. While the AR-15 is used for target shooting and hunting, it also occupies an unusual position in the gun world by account of its modular design that allows for extensive customization.
When the stock of an AR-15 is removed and there is only one grip, it is considered under US ATF (Alcohol, Tobacco, and Firearms) regulations to be a pistol. This allows it to be used with a short barrel, typically in the 6 to 12 inch range, whereas as a rifle the barrel must be longer than 16 inches to avoid special licensing requirements.