Castings, forgings and "from billet" are all excellent means of manufacturing metal components.
Each has enjoyed its time in the sun. In the very beginning of metal working items were hammer forged from pieces of metal produced in early hearths. Bits of metal were hammered into larger piece and was shaped by the blacksmith using a hammer on an anvil. As time went on, and hearths improved, pots of metal were smelted. To get use of this pot of metal, molds were made and items were cast.
Casting of metals is an art. In the early days many castings were flawed by cold spots, voids, slag inclusions and the like. If you were making a cooking pot, these might not be deal breakers. When cannons were cast, they often did break explosively causing great loss of life.
Forging produced a denser product without many of the problems associated with castings. It made a stronger product, that was more homogeneous and had a better surface finish. Most forgings, produce many exterior features to net size and shape. Castings can do the same, but until the advent of investment castings, the surface finish was rough as produced by sand casting. As mentioned earlier, forgings either worked by hot or cold processes force the metallic grain structure into one that flows with the shape of the component. This provides greater innate strength.
"From Billet" is a process where the component is machined out of the "Solid Billet." The billet is either a bar or plate that has been extruded or rolled into shape. The advent of modern CNC machines has made it attractive to use this method to produce small lot size components. The CNC is fast, can run unattended or even in "dark shops" if the tooling and component support this process. Think of machining the firing pin from a billet rod as the same as if you whittled it out of a stick. You know wood has a grain and your shaping the pin from the stick cuts through all that grain structure. Same as cutting from the billet.
Properly designed and manufactured, each process, casting, forging or from billet is well suited to most weapon components. Forging; however, in my opinion is far superior for gun barrels and allows a lighter weight component than either of the other two processes. Receivers can be made using either process to good advantage.
Ralph
