The 80 percent lower represents the easiest and most affordable way to build a functional AR-15 rifle or pistol lower at home, without any red tape and without paying a premium for an off-the-shelf lower at the local gun store. But not all 80 percent lowers are made equal! Which is best, forged, cast, or billet? Let’s break down the three, describe their pros and cons, and help you make a choice on which type of 80 percent lower is best for you.
Forged 80 Percent Lowers
As the name implies, forged 80 percent lowers are made from forged alloy. The alloy in question happens to be the best of the best: Mil-spec 7075 T6 aluminum. This is the same alloy the military uses to build its standard-issue M4s and M16s. If you want the toughest of the tough, a forged 80 percent lower is the way to go.
Now, before you jump on a forged lower, know this: They are a tad more difficult to machine compared to a billet aluminum 80 percent lower. This is simply because the forging process creates a more dense, harder alloy. This denser, harder alloy poses a challenge for the average drill bit and end mill bit. Now, they’re not hard to machine – they just take a little bit more patience, time, and consideration.
Billet 80 Percent Lowers
Billet 80 percent lowers are the gold standard of the 80 lower world. These are considered the most popular, easy-to-machine lowers available. Just like forged lowers, billet 80 percent lowers are crafted from weapons-grade metal alloys, just like any off-the-shelf AR-15. That alloy in question is 6061 T6 billet aluminum.
Billet 80 percent lowers might scratch and dent a bit more easily compared to a forged lower, and billet lowers may suffer from machining mistakes more readily compared to that forged, hardened alloy. However, if you’re a first-time builder, a billet 80 percent lower will be the easiest route to take! Billet 80 percent lowers are great for custom fabrication, too. Billet alloy is more easily worked to create complex shapes. Generally, billet lowers afford owners a more aesthetic finish.
Cast 80 Percent Lowers
We can’t say this more candidly: Cast 80 percent lowers are terrible, unsafe, and you should never buy one. As the name implies, cast 80 percent lowers are crafted from a rough aluminum alloy that’s poured into a molding. The problem with cast lowers is that the casting process creates small air pockets and imperfections in the alloy.
The result is a lower that is structurally not capable of supporting the pressures and rigors of a functional firearm. Cast lowers can often shatter, crack, or even explode. Even during the machining process, a cast 80 percent lower could fail. The result could be metal alloy or bits of tooling flying in your face. No one wants that. Avoid cast 80 percent lowers at all cost.
Which Lower Should You Get?
To keep things simple, we recommend first-time buyers try out a billet 80 lower receiver. The machining process will be made easier, and you can even pick up a Premium Billet 80% Lower with some added features that make final assembly a breeze. Once you’ve mastered the machining process, you should pick up a forged 80 percent lower (trust us, you’ll want to build another one). This will afford you two proudly home-built rifles that offer the best of both worlds! Just stay away from cast lowers. Trust us.DISCLAIMER: If you are new to the world of DIY AR-15 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. 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.