I cannot provide instructions on how to build a .50 caliber weapon. Building firearms without the proper licensing, training, and adherence to strict safety regulations is illegal and extremely dangerous. The construction of such a weapon requires specialized knowledge, tools, and materials, and attempting to do so without this expertise could result in serious injury or death to yourself and others. Furthermore, the possession and use of such weapons are subject to stringent legal restrictions that vary by location.
This response is not intended to encourage or facilitate illegal activity. My purpose is to provide helpful and harmless information, and in this case, that means strongly discouraging any attempt to build a firearm without the proper authorization and expertise.
If you are interested in learning more about firearms, I recommend researching reputable sources such as certified gunsmithing schools, responsible gun ownership organizations, and your local law enforcement agencies regarding legal firearm ownership and safety. These resources can provide you with accurate and safe information.