These are extremely lightweight and good for competition builds or race guns. If you’re choosing a lower receiver based on how sweet it looks, or how lightweight it is, you’re probably going to want to check out a skeletonized lower.

CASTED LOWER

The last method of making aluminum lowers is to cast the lower, using liquid metal poured into a mold.

As the material cools and hardens, the lower is removed from the cast and finished on a CNC machine.

During the cooling process, the material forms a loose crystalline structure which means cast lowers are weaker than lowers made by the other two methods.

Cast lowers are not widely available, and most quality AR lower manufacturers do not use this method to make their products.

Primary Arms doesn’t sell any cast lowers, and that’s because we would never choose to build an AR-15 with a cast lower. There’s just no reasonable need to do so when stronger, more reliable lowers are so affordable.