Forged vs Billet AR Lowers: What’s the Difference?

When building a custom AR-15 from the ground floor, it’s of the utmost importance that you choose the materials that you intend to build upon wisely.

A stripped lower receiver, for instance, is the anchor of your build and the makeup and weight of its materials will greatly determine how your rifle is centered, how it mounts, how it holds, and ultimately how it operates. 

In today’s market, there are countless fabrication options for builders to consider when beginning the project. In some cases, these custom builds include lightweight polymer stripped lower receivers, but our focus will solely be on the differences of the most likely candidates: forged and billet.  

One of the questions you will undoubtedly incur as you begin building ARs is, “What is the difference between forged vs billet AR lowers?”

We’ll thoroughly examine the strengths, weaknesses, similarities, and differences of these two popular methodologies to help you make a more informed decision when choosing a stripped lower receiver for your next AR build.

Ready, set, let’s roll…

What’s a Stripped Lower Receiver?

Let’s start with the basics. A completed lower receiver comes with the trigger assembly, safety selector, mag release, bolt catch, and buffer assembly pre-installed. This type of lower receiver is ideal for shooters who prefer a ready-to-use base, which allows an upper receiver to be mounted with little fuss.

While there’s some room for personalization with these completed receivers, like switching out a stock or grip, the design options are more limited compared to other types.  

A stripped lower, on the other hand, contains the surrounding housing for the fire control group, but is devoid of those required internal components. That said, this customizable stripped variant provides the essential machining, magwell, and the required access points to install a trigger group, attach a grip, fasten a stock, and mount an upper assembly. 

This stripped receiver type provides a blank canvas for discerning builders to carefully pick each component to build the rifle of their choosing. Of course, building upon receivers of this type is both time consuming in terms of assembly and, most importantly, requires structural foreknowledge because the parts must be thoroughly researched to ensure proper fitment. 

No matter the type that’s implemented, the lower receiver is a vital component that serves as the frame for the rifle and is considered by many to be the heart of the AR-15. 

Why Build with a Stripped Lower?

If you’re serious about custom building an AR, utilizing a stripped lower receiver is as good a starting point as you’re going to get.

Beginning a gun project with a stripped lower allows for greater levels of customization, enabling builders to construct a rifle that meets their preferred specifications down to the last component. Moreover, fabricating a rifle in this fashion is often more cost-effective than buying a completed firearm from an FFL.  

What’s more, building an AR from the ground up with a stripped lower is no small feat. Understanding the complexities of gun mechanics and developing the skills thereof requires a considerable amount of patience and attention to detail. 

If you’re a newcomer to rifle assembly, we recommend looking into the bevvy of online tutorials and resources available, or ask someone familiar with the task to shadow you during the build to ensure safety, regulatory compliance, and the proper functionality of the weapon. 

Consider the process—the invaluable skills development and the sense of accomplishment upon your rifle’s completion—the price of admission is more than worth it.

Materials

By far, the most common material used to mold stripped lower receivers is aluminum. The reason for this is that aluminum does not easily show signs of wear because it bonds with oxygen to provide a surface-level protective base. However, an anodized coating is often applied to aluminum to add an extra level of protection against corrosion and pitting. 

There are two different aluminum alloys of varying strengths that are often utilized during the fabrication process of stripped lowers depending on the build: 7075-T6 and 6061-T6. 

7075-T6

One of the strongest aluminum alloys commercially available of the two, the zinc-primered 7075-T6 is prized for its balance of weight, durability and corrosion resistance. This high grade methodology has a greater strength yield, which makes it more resistant to deformation, but also makes it more brittle during the curing process. 7075-T6 is often preferred in the manufacturing of firearms and high-stress aerospace metal.

6061-T6   

A more lightweight alternative, the magnesium/silicon-primered 6061-T6 provides a more malleable, but toughened exterior, albeit with less protection from the elements. What this weaker methodology lacks in strength, it makes up with its superior ease of formation, as the alloyed metal is easier to weld, which makes it ideal for more general purpose applications.

6061-T6 is ideal in the fabrication of certain gun components, automotive parts, and it’s also utilized in construction.    

Forged Stripped Lower Receivers

The forging process begins when a block of highly durable 7075-T6 aluminum is made malleable through high heat and pressure. The resulting metallic product is then hammered into shape via a die mold, which heavily compacts it and makes it stronger. By aligning the grain structure of the molten metal with the shape of the lower receiver, the strength of the aluminum is enhanced, making it resistant to both impact and fatigue.

The newly forged blank is then machined to remove excess debris and create the precise angles and dimensions needed for a stripped lower receiver. This procedure includes milling the magazine well, fire control group cavity, and adjacent pin holes.

Advantages

From a strength-to-weight ratio, forged stripped lower are stronger due to their greater level of molecular density, but they are also generally lighter than their billet counterparts. These innate structural qualities can prove to be advantageous for shooters looking to fabricate a durable, but lightweight AR rifle.

The forging process of stripped lower receivers produces less combined waste compared to other methods, which make it more affordable for consumers. What’s more, forged receivers are more widely available because they have been the standard for both government agency and military deployment, which further supports their functional reliability as compared to the billet methodology.

Disadvantages 

Other than engraving, the cut-and-dry approach of the forging process, there’s little room for any aesthetical touches or personalization that are present in billet stripped variants, which may leave some shooters wanting more out of the appearance of their stripped lower receiver. Furthermore, with such a high tensile strength, forged receivers see little in customization in terms of shape manipulation.  

The overall finish in forged receivers can vary depending on manufacturer and machining process, as some receivers may require further machining to ensure a smooth matte finish. Additionally, in rare instances, forged receivers may not have proper fitment due to imperfections in the mold due to too much or too little excess aluminum removed during the machining process. 

Billet Stripped Lower Receivers

This process begins with a raw billet block of 6061-T6 or 7075-T6 aluminum, but most often it’s the former for its more malleable molecular properties. The block is then milled via a CNC machine to establish exact dimensions and tolerances.

Once completed, the stripped lower is inspected and any imperfections, sharp edges, or burrs are removed to ensure a smooth finish and ease of handling. From there, this stripped billet variant receives a sandblasting or anodized treatment to shore up its protection against corrosion.  

Advantages

From a standpoint of customization, billet stripped receivers can be machined with unique designs, intricate flourishes, and custom features for a more personalized look, but these modification options are not readily available with other methods. Billet-made stripped receivers can also be molded using a wider variety of alloys while still achieving an equal level of durability (7075-T6) and aesthetics (6061-T6), which other premium alloys can do, but not simultaneously.

When it comes to mating a billet lower receiver with a billet upper assembly, the tight tolerances, and smooth finish already instilled in the build quality aid in the AR-15’s proper fitment, shot accuracy, and better protects the rifle’s internals from the elements. A completed billet-made firearm will maintain excellent tolerances throughout, yes, but with a tradeoff of a heavier rifle.      

Disadvantages    

The most standout disadvantage that billet stripped lower receivers face is the cost as compared to the competitive pricing of forged lowers. Likewise, the process of forming billet stripped lowers requires more man-hours to complete and is far more time-intensive than crafting forged lower receivers.

The greater weight of billet receivers versus the more lightweight hold of forged may be a setback for some builders, especially if a lightweight AR rifle is preferred. Furthermore, billet receivers most often lack the grain structure of forged receivers because billet stripped receivers often call for 6061-T6 in order to maintain a high level of customization, which can negatively affect its overall strength threshold.

What about Mixing and Matching?      

Mating a billet stripped/complete lower with a forged upper receiver—or vice versa—can be done.

In some cases, marrying these two methodologies on the AR platform can provide you with the best of both worlds in terms of material strength, customizable real estate, and balanced weight distribution. That said, there are some things to consider when attempting to go that route.

Most importantly, there could be fitment issues when, say, mounting a billet upper assembly with a forged stripped lower receiver due to the differences in design methodology and tolerances, so compatibility between the two must be assured beforehand.

Builders may also find a vast aesthetical mismatch between their upper and lower receiver, leaving them unsatisfied and wanting more of an encompassing theme in their design choices. Lastly, the potential higher cost of joining the two receivers must be taken into account before moving forward.

We recommend that if you’re going to mate a billet receiver with a forged one, do your research and go with the same make and company to ensure similar tolerances and a lifeline of customer service/quality assurance should you need it.

Also, look for online reviews, tutorials, or anything documenting other builders’ experiences to gauge success rates when merging billet components with those that are forged.

But in any other case, we would suggest that you either go full billet or full forged for your AR setup in order to save on possible cost, fitment, or performance issues down the line. 

Which is Better, Billet or Forged?

With most things gun-related, whether to go with one stripped lower receiver over the other comes down to your build priorities, budget, and intended use. 

If you’re looking for a lightweight, but durable profile that can withstand the rigors of moderate to heavy use and remain functional in harsh environments, going with a forged stripped lower receiver is your best bet. We say that because with a forged receiver, you get the nostalgia factor of Mil-Spec without breaking the bank to get it.  

Alternatively, for any specialty build or, say, a trophy gun where money is of little concern, a billet stripped lower is definitely the way to go. If you favor the flexibility of customization over material longevity and want your AR-15 to exude more personal touches and be replete with custom features, albeit with a heavier firearm, you get that and more with the niche design scheme of a billet stripped lower receiver.

Some shooters swear by billet because it allows them to make the gun their own with original textures and designs, while maintaining a comfortable level of material strength and beefiness in handling. Other marksmen just want a military-grade, lightweight AR with a nondescript finish that they can count on to perform at a high level wherever, whenever, so they often roll with forged. 

All that to say, both of these methodologies have their advantages as well as their setbacks. The best way for you to make an educated choice between billet and forged stripped lowers is to examine your needs in terms of your ideal AR-15 loadout and go from there. After all is said and done, in terms of firearms, it’s always going to be about personal preference.

Legal Requirements

While stripped lower receivers don’t function like fully formed AR rifles out of the box, government regulations still consider them to be firearms due to their milled access points. Thus, stripped lowers must be purchased and transferred through an applicable dealer with an FFL (Federal Firearms License), which usually entails a holding/pick-up fee.

Final Thoughts on Forged vs Billet AR Lowers

So, forged or billet stripped lower receivers? That question is best left to you. Only now, you know the differences between the two.

Stay safe out there.

Which type of stripped lower receiver do you prefer in your AR build? Tell us about it in the comments section.

Aaron Basiliere

Aaron Basiliere is a staunch 2A advocate, a firearms researcher, and one of the principal content creators here at CAT Outdoors. He has written in multiple professional capacities for the last 16 years. He has a BA in English Writing from the University of Wisconsin. When not writing for CAT Outdoors he enjoys drinking coffee, watching documentaries, and spending time with his family and friends.