Four Misconceptions about Building an AR-15 from an 80 Percent Lower
There’s a lot of confusion out there about 80 percent lowers. If you’re considering building an AR-15 from an 80% lower, odds are that you’ve heard some of these before, but realistically, these are just simply incorrect. While this may not answer all of your questions about 80% lowers and AR-15s, let’s go ahead and put some of these misconceptions to rest.
Here’s four extremely common misconceptions, in no particular order.
You hear this one a lot. As of the time of writing this, 80% lowers are completely legal. The Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF, for short) is fully aware of the existence of 80% lower receivers, and has published on their website that they are completely legal under the right circumstances.
Based on current federal laws, a lower receiver only becomes a firearm when the fire control cavity area has been machined. Assuming that your 80% lower is an ACTUAL 80% lower, it is fully legal. As long as you are milling the receiver yourself (a gunsmith can’t do it for you), the lower is completely legal.
It is also fully legal to build a weapon from an 80% lower receiver, and you are not required to add a serial number, dependent on your state.
However, once the weapon is completed, it still must be in compliance with any state laws. For example, in California, they recently passed a law that will require any new firearms built from 80% lowers to have serial numbers. Similarly, if there are any regulations about fixed stocks, pistol grips, or lower magazine capacities, your weapon does need to follow those local laws.
This is another common one that is simply not true. Finishing an 80% lower is extremely easy, assuming you have what you need.
To mill out the receiver, you will need an 80 lower jig, the tools that go with it (example: https://www.ar-15lowerreceivers.com/collections/80-lower-jig/products/easy-jig-gen-2-tooling-ar-15-308-jig), a router, a bench vise, and a drill press. Some of them can even be completed with a hand drill.
That is legitimately it. Those are the only things that you need to turn that hunk of metal into a fully functional AR-15 lower receiver. With newer jigs, this can be accomplished in less than an hour. If this is your first attempt, or you’re not that mechanically inclined, it may take slightly longer, but it is still an afternoon project.
Now, for turning that lower into a weapon…
Yet another misconception. Building a weapon from an 80% lower receiver is no different than building a weapon from a serialized lower receiver.
If you’ve never done this, it is similarly pretty easy. You’ll need a lower parts kit (https://www.ar-15lowerreceivers.com/cmmg-lower-parts-kit-butt-stock-buffer-tube-assembly-ar-15/), an upper receiver, a barrel, a handguard, a bolt carrier group, and a charging handle. Not all lower parts kits come with a buffer, buffer tube, and stock, so you may have to buy those separate. To make matters even easier, you can buy an upper receiver that comes with a bolt carrier group, charging handle, handguard, and a barrel, all pre-installed for you.
Now, as far as actually installing all of these parts, it’s really pretty simple. You’ll need a few tools, such as an AR-15 armorer’s tool (https://www.ar-15lowerreceivers.com/castle-nut-wrench-ar-15/), a punch set, a roll pin punch set, and a rubber/brass hammer, but it really is pretty easy. If you’ve got any questions about how to actually install the parts, there are plenty of YouTube videos that show you exactly what you need to do.
Another idea that is simply incorrect. A quality 80% lower such as this one (https://www.ar-15lowerreceivers.com/80-lower-black-1-pack/) or this one (https://www.ar-15lowerreceivers.com/premium-black-80-lower-billet-fire-safe-engraved-1-count/) are made from the exact same metals as their full up counterparts. There is absolutely no difference in the structural integrity of the lower.
Assuming that you take your time to mill the receiver probably, your 80% lower receiver will last for as long as any other lower receiver out there.
While this is certainly just the beginning of the misconceptions surrounding 80% lowers, hopefully we can put these to rest. What other misconceptions have you heard?