What is a billet or what are billet lowers? A billet is a term for a solid block of metal with no features at all, almost as raw as metal can get. A forging on the other hand is a piece of billet that has been pounded into shape by a die on a forging press. It requires less machining because it has been shaped into a receiver blank, and has the advantage of the metal grains following the shape of the part. But that really doesn't mean all that much except to your wallet. Forgings offer significant cost savings and no real drawback.
Our AR-10 lowers are both offered as forged lowers and billet lowers depending on what your price range is. Cosmetics aside, there isn't a huge difference between billet aluminum and forged aluminum other than price and freedom of design. With that said, the billet lower receiver does have the advantage of having all sides machined in the milling machine and in some cases allows you to add features like an extremely flared magwell or an ambidextrous bolt catch. A billet lower receiver normally is purchased because of it's cosmetic appeal. Other manufacturers offer a billet lower receiver that may suit your needs, we only offer billet aluminum options in the TM-22 and AR-10 platforms. Some forgings are designed for companies and include those features like the flared magwell as well. Again, it really is a draw, there is no clear winner here.