Well I couldn't have my halftrack be defenseless so I built a 1919A4 to mount on it. It is perfectly legal to build your own semi-auto firearm. Many thanks go to the 1919A4 website and forum for sharing their knowledge, I couldn't have done it without them. After getting the parts milled and the sideplate made and received from the FFL it only took about 6 hours of actual work to put it all together. Number two is currently in the works.