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AR Lowers: Cast Aluminum vs Billet Aluminum vs Forged Aluminum

Combining adequate density and a unique ability to resist corrosion, aluminum has become a well used alloy within a multitude of industries. Made popular by the aerospace sector, aluminum has become a vital component within most types of manufacturing.

Various types of aluminum are also used in the manufacturing of AR-15 uppers and lower receivers. Whether cast, billet or forged, aluminum serves as the material most AR-15 upper and lower receivers are manufactured from.

Cast Aluminum vs Billet Aluminum vs Forged Aluminum: What The Difference?

If you’re new to the landscape of custom AR-15’s, you’ll soon be introduced to terms that depict the various types of aluminum used when manufacturing the AR-15 upper and lower receiver. Whether ‘cast, billet or forged’ aluminum, you should become familiar with the differences in each before purchasing your upper or lower receiver.

  1. Cast Aluminum Lower Receiver

Cast aluminum usually refers to the method of forming a lower receiver by using a mold. By pouring molten aluminum into a ‘lower shaped’ mold, the lower is formed when the aluminum solidifies. The casting is then removed and a CNC machine is used to finish the manufacturing process.

By using a casting process the manufacturer can offer a functional and economic lower receiver. This process can also offer the best synthesis of mechanical properties when A380 aluminum is used during the casting process.

While there has been less than ethical manufacturers who became known for their poor casting processes, if the lower is cast properly and attention to detail is adhered to, a cast lower receiver will provide quality and reliability for most types of AR’s.

  1. Billet Aluminum Lower Receiver

When a manufacturer refers a lower receiver being manufactured from billet aluminum, they are usually referring to a receiver that has been machined from ‘bar stock’. The ‘bar stock’ is formed by extrusion or in other words, from being rolled into a particular shape and size. A piece of the extrusion is then used by the manufacturer and machined on a CNC machine into a functional lower receiver.

Billet aluminum lowers are considered to be the best looking of all lowers. Due to the ability of the CNC machine to mill fine lines and particular designs, billet lowers are known for their aesthetics. While looks do little for overall performance, some like the added finesse when building a custom AR.

Take a look at this awesome diagram that shows the difference between Billet and Forged.

  1. Forged Aluminum Lower Receiver

Forged aluminum refers to a lower that has been ‘hammered’ into forging dies to shape the aluminum into its specified contour. The aluminum is subjected to repeated force, which in turn ‘forges’ the shape of the lower receiver. Once the forging is complete, it also is finished on a CNC machine.

A forged lower receiver is the strongest of all lowers. Metallurgists agree that the forging process results in the aluminum having continuous grain characteristics, which results in the lower becoming stronger than billet or cast aluminum.

This AR-15 Lower Receiver Diagram does a nice job of explaining the difference between Billet and Forged.


Is there a right or wrong choice when purchasing a lower receiver? Yes and no! A cast lower receiver from a reputable company will serve most AR builders just fine. A forged lower receiver from a less than reputable company may not be a good choice. Ultimately, the manufacturer’s reputation and personal preference will be the deciding factors.

While there are a myriad of opinions as to which lower will offer the best possible performance, today’s manufacturing processes allow manufactures to provide high quality lowers no matter the type of aluminum.

Vision Armory welcomes any questions you might have regarding our lower receivers or our manufacturing process. Please feel free to contact us anytime. You can also read more articles on building an AR-15 in our resource center.

Be safe, have fun and support The Second Amendment!

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