Posted by on 9/17/2021 to
Lower Receivers are, legally, the most important part of the AR. That is because they are the only part of the AR that is considered to be a firearm by the federal government. For that reason, they have a serial number on them. Then there are 80% Lower Receivers. These do not have a serial number because they are not considered a firearm until the necessary modifications are made.
There are many materials that Lower Receivers can be made from, though most are made from aluminum. They can also be made from steel, titanium, and polymers. It is possible to make it out of any solid material. There have been examples of Lower Receivers made out of wood, with metal internals. You could make one out of butter, though I don’t see it lasting too long with use. It is just a shape, and you can use any material to make that shape, though it might not last as long as those made with traditional materials. When it comes to finding the sweet spot where quality and value meet, polymers can be a good choice. Polymer is not considered to be as strong as aluminum, though its other advantages might tilt your decision that way. For example, a polymer will never rust and usually weighs less than metal. Aluminum is by far the most popular choice, it is the original choice, and probably the material that most consistently provides the best quality at the lowest price.
There are different types of aluminum, and all the ones currently on the market are very durable and will cause your Lower Receiver to last longer than other integral parts of your AR. The two most popular types are 6061-T6 and 7075-T6, 6061-T6 works great, though 7075-T6 is technically stronger. In fact, 7075-T6 is one of the strongest forms of aluminum and can match most steel alloys with less weight. The ways these materials are formed into the shape of the Lower Receiver can also affect the strength.
You really don’t see cast aluminum on AR parts these days, there are better ways to do it now. Billet is a very popular way to go because it is strong and highly customizable. You can produce Lower Receivers with a lot of stylistic design this way. Billet takes a solid bar of aluminum and CNC machines it. If the Lower Receiver deviates from the basic shape, there is a good chance it is Billet. Billet pieces do tend to cost more, but if you want your AR to be unique, then the extra cost could easily be worth it. If all you care about is strength, then you may want to get a forged Lower Receiver. This also takes a solid piece of aluminum which is then hammered into the shape of the Lower. It is then finished with a CNC machine though just to finish it up, put on the fire control labels for example. There are some beautiful examples of unique forged Lower Receivers, though there is still not quite the range in styles that you’ll find with Billet Lower Receivers. Under normal circumstances, any type of aluminum Lower Receiver produced these days should last for a long time. There are not many reports of aluminum Lower Receivers of any kind breaking under normal firing of the rifle.
80% versions are in the same basic shape that any lower receiver is, it just doesn’t have the necessary holes machined into it. That’s what’s meant by 80%; it is 80% done. Just add the holes, and it is now a 100% lower. Of course, you still need to add the Lower Parts Kit so you get the trigger and safety selector and all of that other stuff. Depending on where you live, you also might need to register or get it serialized. 80% lowers are great if you like working with your hands or want to turn building your AR into an enjoyable project.
Whatever you choose when it comes to your Lower Receiver, be sure to check out our selection here at Davidson Defense. Our options do change from time to time as we continually work to make sure we are getting you quality items at great prices. When we find good deals we pass them on to you. For individual Lower Receivers look under stripped lowers and 80% lowers. We also offer lower build kits that include the lower parts kit, buffer system, and stock.