When deciding on a 80% lower to begin a build, there is a dizzying array of options out there and the benefits of one over the other are not readily apparent, or are shrouded in marketing terms so as to appear better than the rest.
The three popular options today are 6061-T6, 7075-T6, and reinforced polymer. When it comes to overall strength, 7075 beats out 6061 with 60% greater tensile strength and fatigue strength, and 50% greater shear strength. This greater strength results from a greater hardness, which in turn results in 7075 being more susceptible to fracturing upon sharp impacts than 6061. Also, keep in mind that 6061 is going to be significantly easier to machine due to it being softer than 7075. And then along comes polymer. Obviously a puny runt when compared to the aluminum alloys, why even enter as a contender? Because considering the stresses that the regular use of an AR places on a lower, we see that the polymer is more than sufficient while offering an extremely lightweight option. Not to mention, it machines like butter, so if all you are doing is cutting polymer lowers, your bits will last for damn near ever.
Billet and cast are the two varieties that jump to mind. You can obtain a cast lower, but the frequency at which they appear on the market kinda leaves them as nolo contendere. Billet will leave you with much cleaner lines and a greater overall aesthetic, while forged will give you a marginally stronger lower. Also keep in mind that a great deal of forged lowers are finished on a CNC mill for final detail and result in an identical finish as a billet milled lower. So if you are after a certain look for your build, don’t let forged discourage you.
Raw or anodized, really comes down to whether or not you are going to give your lower an aftermarket finish. If you are planning on having a Cerakote finish applied, I would say, get a raw 80% lower.But if you are just going to leave it as is, an anodized 80% lower finish is a good idea, especially on a 6061 lower as they are slightly more susceptible to corrosion than their 7075 counterparts.
There are a ton of features and add-ons that exist on 80 lower receivers. From purely aesthetic to strictly functional, some will add significantly to the cost and others are included as standard. Engraved fire/safe is one of the included features that a lot of manufacturers are adding as a standard feature.Now while it won’t make your gun shoot any faster, farther, or straighter; it is a sign that manufacturers are paying attention to the details and it adds to the finished look of your project.
Last, but not least, warranty. If the lower you are looking to buy doesn’t come with a 100% satisfaction guarantee, then don’t buy it. Never take a chance on a product that isn’t backed by a promise. At AR-15 Lower Receivers, we promise that if anything is not to your satisfaction with any of our products, we will make it right.