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The Difference Between an 80% Lower and Upper

Posted by Jordan Vinroe on Oct 22, 2019

Building a rifle at home is a fun and satisfying way to make sure you have the protection you need. However, there are a lot of components needed to design and assemble a fully functional weapon. One term you often hear when it comes to DIY firearms is 80% lower and upper receivers. These are the most critical components needed for a successful build. Let’s look at how these two pieces are different, and how you use them to create a firearm that looks and operates just like ones available from the manufacturer:

man holding 80% lower and upper gun

What is a Lower Receiver

Every DIY firearm build starts by focusing on the lower receiver. While you will eventually need both the 80% lower and upper receivers, starting with this solid base ensures success with your firearm build. The lower contains the fire control group of the rifle:

  • Trigger
  • Disconnector
  • Hammer
  • Fire selector

Lower receivers are marked with the firearm’s serial number and manufacturer’s name. Because of these markings, finished receivers must be purchased through a licensed firearm dealer.

That is not the case for 80% lower receivers. Since these unfinished parts are not considered a firearm by the Bureau of Alcohol, Tobacco, and Firearms (ATF) because they need precision milling in order to be functional.

What is an Upper Receiver

To create a truly custom firearm, the component that DIY builders focus on is the upper assembly which is also known as the upper receiver. The upper receiver has a modular design which makes it easy to swap and exchange different parts from the charging handle to the barrel and rail system. You also have the ability to purchase a full kit to build the upper receiver. You combine  uppers compatible with a variety of brands to create a one-of-a-kind assembly with unique or retro accents.

 machine gun aiming

Legal Details about Receivers

Knowing what 80% lower and upper receivers are is only part of why you should consider taking on a build to create a finished firearm.

At the start, 80% receivers might just look like a chunk of metal. But it is legal in most states to machine these pieces and create a firearm comparable to a mass-manufactured piece. With a jig kit, drill press, and a bit of talent, you can easily create your own custom firearm from build kits. Best of all, they allow you to own a firearm without a background check or even a serial number.

With some help from the experts at JSD Supply you can learn how to finish 80% lower and upper receivers to build a firearm right in your own garage.  Contact us today to learn more about receivers and all of the other components needed to design your own rifle.