The AR-15 is comprised of several core components that play a vital role in its overall functionality, but the lower receiver is by far one of the most important. Simply put, without one, you won’t be able to have an AR-15, as it serves not only as the anchor point for which all other parts are attached, but the serialized portion of the firearm.
Being as important as they are, there are a lot of lower receiver options to pick from. On one hand, you have the tried and true forged lower, offering simplistic utility in a design that’s essentially remained unchanged for several decades—and on the other you have the more modern billet lower, which often features unique designs and added comforts like ambidextrous controls.
While we touch on these lower variants in our best AR-15 lower receiver guide, the question still remains—what’s the difference between forged and billet lower receivers?
Breaking down the Basics
If you’re new to AR-15s, the lower receiver is the primary component needed for a rifle build. Because of how important it is, you need to take a lot into consideration to make sure you choose the right one when you’re getting ready to start a new build, whether it be for competition or defense—which we touch on in our guide, “Building a Home Defense AR-15“.
Although the number of lower receiver options seems endless, nearly all of them fit into one of two categories: forged and billet. Both lower types are created from the same aluminum base, but they have different manufacturing processes and offer their own unique advantages.
Forged Lowers
Forged lowers are, by far, the most common type of lower receiver on the market. As their name suggests, these lowers are forged into shape and later finished with either anodizing or some other coating. Most of the time, forged lowers follow the mil-spec standard as far as design goes, so they’re simplistic in their designs, coming with the bare essentials so-to-speak.
Still, their designs can vary, as options like the LMT MARS-L bear resemblance to a standard mil-spec lower but offer fully ambidextrous controls. Additionally, Daniel Defense’s newer DD4 RIII rifles utilize a similar design, coming standard with a forged ambi lower receiver.
For the most part though, forged lowers are going to feature a standard mil-spec design. While they lack the variety that’s allotted by billet lower receivers, they more than make up for it with their low cost. Forged lowers can vary in price depending on the manufacturer, but they can cost as little as $50 in some instances, making them a solid choice for all rifle builds.
Billet Lowers
Billet lowers are another common choice available when shopping for a new lower. Instead of being forged into shape, billet lowers are made by milling an aluminum blank into shape, giving manufacturers much more leeway in terms of design. These lowers often have unique designs and features such as ambidextrous controls, built-in folding stock mechanisms, skeletonized frames, and more. Keep in mind that these lowers manufacturers don’t match the mil-spec standard like most forged lowers. However, billet lowers are usually compatible with most, if not all, standard AR-15 lower receiver parts, though there may be some variance at times.
Not all billet lowers are made equal, with their designs varying across different manufacturers. For instance, Aero Precision’s M4E1 lowers are strikingly similar to mil-spec ones, while options like the Radian Weapons A-DAC Lower Receiver have a more unique design, featuring their dual-action catch system and fully ambidextrous controls. Also, many billet lowers are sold in sets include both the lower and a matched upper receiver, ensuring a precise fit with tight tolerances
Despite their benefits, the manufacturing process for these lowers takes considerably longer than forged options, making billet lowers a more expensive option comparatively. Depending on which model you look at, their price can range from around $250 to upwards of $500+.
Strength, Durability, Performance, and Functionality
When deciding which lower to go with for your next AR build, you can’t really go wrong with either option, but both have distinctive characteristics that make them better suited for different needs.
Strength and Durability
Most AR-15 lower receivers are made from forged 7075-T6 aluminum, a strong and lightweight material. Forged receivers are renowned for their strength and durability, which is owed to their manufacturing process. By forging the aluminum instead of milling it out, the grain of the metal is aligned to the shape of the receiver, giving it optimal strength for resisting impacts and rough use. Billet lowers, on the other hand, don’t have the same grain alignment since they’re milled, leaving them slightly weaker pound-for-pound.
That said, they still make for an incredibly durable receiver option. Both forged and billet lowers perform excellently in harsh conditions, and neither is likely to be your rifle’s main point of failure.
Performance and Functionality
At their core, both forged and billet lowers accomplish the same goal. They both house many of the rifle’s controls and critical components, but they offer different degrees of utility.
As we mentioned above, forged lowers most often use a relatively simplistic, mil-spec design. These lowers are compatible with basically everything found in AR-15 lower parts kits but aren’t always compatible with select ambidextrous ones.
For left-handed enthusiasts, these lowers aren’t impossible to use, but it does require you to alter your grip and adapt to perform each of the rifle’s core functions. While forged lowers can have ambidextrous controls, the vast majority of them don’t. Billet lowers, however, often do.
Another critical point of concern is upper compatibility. Mil-spec lower and upper receivers, regardless of their manufacturer, are made to be ‘in-spec’, so it’s easier to mix and match different uppers and lowers together and still have good fitment. Billet receivers are often made to match a specific upper, so they aren’t always compatible with different uppers. While they might match up well and be usable, the tolerances could be tight or loose.
Choosing Your Lower
When you’re shopping around for a lower, there’s two routes you can go down. You can either opt for a stripped lower, or a complete one.
Stripped lower receivers are exactly as their name suggests, stripped of all components. These lowers are best for enthusiasts who prefer to build their rifles, as these lowers give you full control over what parts go into the result. Stripped lowers tend to be a more budget-friendly option, although they do come with the caveat of needing to be assembled.
Complete lower receivers come with all of the necessary components pre-installed into the lower receiver. These options are best for those looking for a simple and ready-to-go lower that can be quickly paired with an upper. These lowers can vary quite drastically in price depending on the manufacturer and what parts go into the lower, but for the most part, you can find complete forged lowers for around $150 to upwards of $350+.
Regardless of which route you go, we recommend familiarizing yourself with the ins and outs of your lower. Our guide on how to assemble an AR-15 lower goes over the build process step-by-step, providing crucial knowledge that can help you with making upgrades or repairs, whenever necessary.
Conclusion
An AR-15’s lower receiver is one of the most crucial components in any rifle build, serving as the keystone for all other parts.
With a forged lower receiver, you get simplicity in a design that’s been time-tested and vetted, with several manufacturers producing both lowers and unique parts for them. Billet receivers, in contrast, offer more unique designs, with them often coming equipped with specialty components. Plus, they pair exceptionally well with their matched uppers.
At the end of the day, both lower options accomplish the same goal but offer different degrees of utility. Ultimately, the best lower is the one that meets your needs and goals best, so be sure to take time to evaluate each possibility to see if it has everything you want.
