A new bullpup rifle was developed by Darkstar Weapons Systems, known as the XBR-223(eXpiremental Bullpup Rifle, .223 caliber). The U.S. Military tested the rifle and soon started issuing the weapon to the Navy SEALs as the Mk. 54. Soon after, numerous other units were issued it as the U.S. Model 478 Adaptive Weapons System, Rifle , 5.56 NATO, A.K.A. M478 AWS-R. After several years of service, there were several different countries wanting to use the rifle, including China, Germany, France, and Canada.