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80 PERCENT LOWER: FORGED VS CAST VS BILLET

80% lowers represent the easiest, most affordable way to build an AR-15 from scratch – you get to save some cash by avoiding the local gun store, and you get to make that new black rifle (or pistol) to your exact specifications. But which 80 percent lower should you spring for, first? With so many options and so much information available, it can get confusing. Today, we’re breaking it all down for you by comparing all three 80% lowers: Forged vs. cast vs. billet!

#1: 7075 T6 Forged 80% Lower

Forged 80% lowers are formed under intense heat and pressure by compressing a large hunk of aluminum alloy into a roughly shaped lower. Once forged, the lower is then machined to clean up forging markings and surface imperfections.

Forged 80% lowers are made from mil-spec 7075 T6 aluminum, an alloy favored by most militaries for its durability, surface hardness, and relatively low weight. Forged 80% lowers are the most robust, but machining them takes more time. Forged 80% lowers also eat up tooling more quickly, so be sure to have spare drill bits and end mill bits available.

#2: 6061 T6 Billet 80% Lower

Billet 80% lowers are the crowd favorite for a number of reasons, though mostly because they’re the easiest to machine. Billet lowers are cut from a large block of aluminum alloy into their final shape, rather than being forged.

Billet lowers are lighter in weight than forged lowers. They are not as rugged as forged lowers, though many store-bought AR-15s are made from billet. If you’re looking for an 80% lower with some unique aesthetics or ergonomic features, you’ll likely need to invest in a billet lower – be sure to check out our Premium Billet Lower as an example! We recommend choosing one of our billet 80% lowers for your first build if you’ve never machined an 80 lower before.

#3: Cast Aluminum 80% Lower

Cast lowers are created by pouring molten aluminum alloy into an AR-15 lower receiver mold. Although some builds have been successfully created using cast lowers, we advise against machining and assembling any firearm with one.

Cast lowers can often suffer from imperfections during the mold pouring. Pockets of air, stress fractures, and other imperfections can lead to an 80% lower that is weak or prone to cracking or shattering during the machining process. Catastrophic failure can occur when firing, possibly resulting in injury or death.

Although some advocate the merits of machining cast lowers, most cast and forged lowers can be bought for similar prices.

80% Lower Finishes

All our forged and billet lowers come available with a traditional mil-spec, Type III Hardcoat Anodized finish! If you want to save even more cash and give your finished rifle or pistol your own design, check out our raw 80 percent lowers. Found a blemish while machining? We sell touch-up Birchwood Casey Aluminum Black touch-up! We recommend investing in a bottle four your build project.


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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