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A Guide to Buying Your First 80 Percent Lower

With so many 80 percent lowers available, it’s almost impossible to figure out which one you should buy to complete your first AR build. What does it even take to finish an 80% lower? Are they all finished the same way? Which caliber should I build first? Rifle or pistol? Billet or forged? Let’s answer all your questions right now: Here’s a guide to buying your first 80 lower!

“What’s an 80 lower?”

Great question! It’s easy: An 80 lower is a hunk of aluminum alloy that isn’t quite yet an AR-15 stripped lower receiver. It’s 80% finished, and you complete the last 20% with some basic hand tools and an 80 lower jig.

Eighty lowers rock because they allow you to save a ton of cash in the AR market, and they require no paperwork or FFL stuff to own one. If you can legally own a gun, you can build an 80% lower.

The Legalities of the 80 Lower

We’re not lawyers, so read up on your local and state laws first, but here’s the short-n-sweet: Building a firearm at home is 100% legal with no FFL transfer, no background check, and no waiting period, as long as it’s for personal use and not for sale. You don’t need any paperwork under Federal law.

Some states (like California) will require you to adhere to certain guidelines. For example, you’ll need to serialize your lower before building it into a legal firearm in CA. Again, your state legislatures and municipal websites will help you confirm what you need to do before building.

Types of 80 Lowers: Material

There are three types of 80% lowers: Billet aluminum, forged aluminum, cast aluminum (which you should never buy) and polymer.

Billet 80 lowers are the easiest to machine, and they’re generally the most popular. Billet 80 lowers are cut from 6061 T6 billet aluminum blocks, and many off-the-shelf AR-15s are made from billet to save weight.

Forged 80 lowers are the top dogs of the mil-spec world. Forged from 7075 T6 aluminum, forged 80 lowers are made the same way the U.S. military likes their service rifles. These lowers are more difficult to machine, but they’re also the most rugged.

Cast 80 lowers are inexpensive, low-quality, and dangerous. Cast lowers are poured into molds, often resulting in pockets of air and hairline cracks. These imperfections can have explosive, even deadly consequences during firing and even while machining. They should be avoided.

Polymer 80 lowers are made from a plastic like most polymer handgun lowers. They’re very easy to machine and often require even less experience and care during the machining process, though they may not hold up to repeated abuse like a mil-spec rifle.

Types of 80 Lowers: Calibers

80 lowers are happily available in nearly every popular caliber! Standard 80 lowers are chambered in 5.56 and .223, and all our 80 lowers feature M4 feed ramps for guaranteed reliability. Newer 80 lowers are available in 9mm and 300 BLK, making them a popular choice for those interested in building an AR pistol or AR-15-based SBR.

Interested in building an AR chambered in .308 using an 80 lower? Read up first: The AR-10 is not a standardized platform, and many off-the-shelf AR-10s are actually built using the DPMS platform. The Armalite AR-10 platform is not interchangeable with the DPMS platform, and care should be taken when ordering any .308-chambered 80 lower to ensure you’re buying the right platform for your internals and upper receiver.

We currently DPMS Gen 1 AR-10 80 lowers and we also offer the required parts kits, uppers, barrels, and accessories so you can complete your new rifle!


DISCLAIMER: If you are new to the world of DIY gun building, you likely have a lot of questions and rightfully so. It’s an area that has a lot of questions that, without the correct answers, could have some serious implications. At 80Lower Jigs, we are by no means providing this content on our website to serve as legal advice or legal counsel. We encourage each and every builder to perform their own research around their respective State laws as well as educating themselves on the Federal laws. When performing your own research, please be sure that you are getting your information from a reliable source.


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