The term “lower receiver” gets tossed around a lot. But exactly what is a lower receiver? First, some basics. The lower receiver is the part of an AR-style rifle that contains the serial number. Generally made of aluminum, it’s that part that all the other parts connect to make the rifle function. Because of this, purchasing a stripped lower has to go through an FFL (Federal Firearm License) dealer.

Are There Different Types of Lower Receivers?

Where it gets a little more confusing to some is when you add the word “stripped.” A stripped lower receiver is like the base of a Lego project. It’s ready for you to start connecting your desired components in your custom rifle build, and they all attach to the stripped lower receiver. 


There are unfinished, or "80 percent" lowers that still require machining work, and these are not generally complete enough to qualify as a firearm. (Photo: Chris Eger/

Of note: a stripped lower receiver should not be confused with an 80-percent lower receiver. They are not one and the same. An 80-percent lower receiver is an unserialized block of aluminum or polymer that requires drilling and other modifications to have it set up as a lower receiver. 

Why Buy a Stripped Lower Receiver?

Why would you use a stripped lower receiver versus a complete lower? In a word, customization. Hand selecting the components for your lower gives you more control of your build. While a complete lower is fast and easy because the components are already set up and attached, a stripped lower allows you to add your choice of components to your rifle. 

Of coarse, one of the best reasons to get a lower kit is to customize the lower to your needs, like removing the stock trigger on the right for a Gucci RMT one, left. (Photo: Paul Peterson/

By starting your build using a stripped lower, you’ll have the ability to select what type of stock/arm brace you prefer, your fire control group (aka the trigger mechanism), magazine (and therefore which caliber your rifle will be), and buffer assembly. To me, being able to pick my preferred trigger makes using a stripped lower worth it, all of the other customization is just icing on the cake!

What Are Qualities to Look for in a Lower Receiver?


Rainer Arms Lower
Good build quality is important, but you can also pick something that appeals to your personal tastes like this Rainer Arms lower. (Photo: Rainer Arms)

So, what do you look for in a stripped lower receiver? Quality billet-aluminum construction will keep your rifle’s weight down while providing a strong, solid lower. Just like a house, a good foundation will give you a solid build. Lowers that have been cast or are made of a different material tend to be lower quality, and this matters when you want your build to be accurate and reliable.  

PDX Upper
A lower does, naturally, need an upper. Which is just another way to really make your build yours. (Photo: Taylor Abney/

While most lowers on the market these days are made from aluminum, polymer lowers do exist. Research what you’re buying and make the decision that makes the most sense in your situation. For me, it will always be high-tensile-strength aluminum. Buying a stripped lower from a well-known manufacturer means you won’t go wrong.


At the end of the day, choosing to build your AR-style rifle using a stripped lower receiver gives you not only full customization as to what components your rifle ends up being constructed with, but many times it will end up saving you a little bit of money, too. Assembling your new rifle this way will let you be intimately familiar with the inner workings of your build.