AR-15 Lower Receivers: Materials, Choices, and Quality

When embarking on the journey of building or upgrading an AR-15, a crucial decision lies in selecting the appropriate lower receiver. The AR-15, with its deep-rooted history spanning multiple generations, has led to an expansive range of options available in the market. These range from the traditional MIL-SPEC designs to the modern, ambidextrous, and visually appealing variants. Choosing a lower receiver involves carefully considering its manufacturing process, the materials used, and weight factors, all while keeping in mind one’s budget and functional requirements. Let’s delve into the development and nuances of AR-15 lower receivers. We’ll also highlight some notable offerings available in the market. Here’s a guide for those new to the AR-15 world, those considering an upgrade, or those simply keen on enhancing their knowledge.

Exploring Lower Receiver Materials

A closer look at lower receiver materials reveals three primary types: cast aluminum, billet aluminum, and forged aluminum.

Cast Aluminum

The manufacturing process for cast aluminum is relatively simple. It entails pouring molten aluminum into a mold. Once cooled, the resulting lower receiver undergoes final machining.

The liquid state of the aluminum during casting leads to a product with a somewhat loose crystalline structure. This method results in the least sturdy product among the three main aluminum processing techniques.

However, it’s worth mentioning that despite cast aluminum being perceived as the least strong among the trio, it offers sufficient strength for the lower receiver to operate safely and dependably. Still, when it comes to preferences, it’s often viewed as the less preferred method for crafting aluminum components.

Billet Aluminum

Billet aluminum lower receivers start their journey as a solid block of aluminum, reminiscent of how a sculptor begins with a block of marble. This block is transformed into a finely crafted product through a series of precision machining operations.

Working with billet aluminum can be likened to metal sculpting, offering several advantages over the casting method. Due to their solid nature, billet lowers possess enhanced strength and showcase a superior finish.

For those aiming for a unique firearm aesthetic, billet lower receivers are ideal. Their design allows for extensive customization, enabling manufacturers to introduce distinctive features such as uniquely shaped magazine wells, integrated trigger guards, and specialized machining for weight optimization.

The creation of billet lower receivers primarily relies on CNC (Computer Numerical Control) machining. In this method, automated precision tools intricately shape a solid aluminum block, facilitating the production of detailed and highly personalized designs.

While billet lowers might carry a heftier price tag, their adaptability and visual allure make them a favorite among many. These receivers, crafted from billet aluminum and shaped by CNC machinery, are known for their crisp lines and the ability to achieve standout designs. Some aficionados even push the boundaries of design with these.

It’s important to highlight that although billet lowers are often perceived as less robust than forged lowers, this difference is typically invisible to the average user. They offer commendable durability and are unlikely to succumb to premature wear or damage. However, some uniquely designed billet lowers might have specific compatibility constraints. Therefore, ensuring their compatibility with standard MIL-SPEC components is crucial, especially if one intends to match them with a particular billet upper receiver.

Understanding 7075-T6 Aluminum

Two prominent contenders emerge in the spectrum of aluminum alloys used for lower receivers: 6061-T6 and 7075-T6. The primary distinction between these two lies in their strength and resistance to corrosion.

7075-T6 is characterized by its remarkable strength, surpassing 6061-T6 by almost double in this aspect. This difference in strength is reflected in the price, with 7075-T6 generally being the pricier of the two. However, it’s essential to recognize that 6061-T6 offers enhanced corrosion resistance compared to 7075-T6. While this resistance can be a significant advantage, its relevance might vary based on whether the receiver retains its natural aluminum appearance or undergoes specific finishing processes.

When planning your firearm assembly, balancing the need for superior strength against budgetary constraints is wise. The gap between 7075 and 6061 is relatively narrow in the current landscape. Nonetheless, many opt for the added assurance of 7075-T6’s robustness, making it a favored choice. Notably, 7075-T6 aluminum is frequently used in aerospace industries due to its outstanding strength-to-weight ratio and resilience, further emphasizing its reputation for dependability and longevity.

Complete Lower vs. Stripped Lower

Are you embarking on your first firearm project? You’ll likely encounter two primary options for lower receivers: stripped and complete. The inevitable question is, “What differentiates the two, and which is the better fit for me?” Let’s break down the distinctions to guide your decision.

Stripped Lower Receivers:

At first glance, stripped lower receivers might seem incomplete. They lack several vital components required for a fully operational lower receiver, such as the trigger, buffer tube, buffer, and stock.

So, why might one opt for a stripped lower receiver, given these omissions?

• Customization Galore: Stripped lowers offer unparalleled customization potential. You’re in the driver’s seat, handpicking each component to align with your vision.
• Budget-Friendly: Typically, stripped lowers are more wallet-friendly than their complete counterparts, making them an attractive option for budget-conscious builders.
• Deep Dive into Mechanics: Assembling a stripped lower offers a hands-on learning experience, granting a deeper appreciation for your rifle’s mechanics.

However, stripped lowers come with challenges:

• Labor Commitment: Crafting a stripped lower demands time and meticulous attention to detail, as each component requires careful installation.
• Tool Dependency: Essential tools, like punches and wrenches, are a must-have for assembling a stripped lower.
• Technical Know-How: A foundational understanding of firearm mechanics is crucial for a successful stripped lower assembly.

Complete Lower Receivers:

Conversely, complete lower receivers are ready to roll outfitted with all essential components. With a complete lower in hand, pairing it with an upper receiver is all that stands between you and a fully operational rifle.

Benefits of a complete lower receiver include:

• Utmost Convenience: Ideal for those short on time or lacking the expertise or tools for a stripped lower assembly.
• Time Efficiency: Pre-assembled components translate to significant time savings.
• Assured Compatibility: Components in a complete lower are designed to function seamlessly together, eliminating compatibility concerns.

Yet, complete lowers have their limitations:

• Customization Constraints: The pre-assembled nature restricts your ability to tweak individual components.
• Price Premium: The convenience of a pre-assembled unit often comes with a higher price tag.
• Missed Learning Opportunities: An already-assembled unit means fewer chances to delve into the intricacies of your firearm.

The decision between stripped and complete lower receivers boils down to individual preferences, expertise, and the desired balance between customization and convenience in your firearm project.

AR Lower Receiver Sets

In the vast landscape of AR lower receivers, Faxon‘s products have garnered attention for their quality and design. Let’s delve into one of their standout offerings.

Faxon X-Tra Lite AR-15 Receiver Set

The Faxon HyperLite AR-15 Receiver Kit is a notable choice for those aiming for a lightweight yet robust build. Building upon the foundation of their acclaimed forged receiver set, this kit emphasizes a balance between aesthetics, functionality, and durability while significantly reducing weight.

Key Features:

• Weight Efficiency: When equipped with an ejection port and dust cover, the kit weighs a mere .96 lbs. This is 2.08 ounces lighter than Faxon’s standard forged receiver set.
• Precision Engineering: The inner bore is refined to enhance the bolt carrier group’s action, promoting smoother operations.
• Design Choices: The forward assist has been omitted for a cleaner look, while the skeletonized Picatinny Rail, with manually engraved T-marks, adds a touch of craftsmanship. The skeletonized shell deflector further trims the weight while ensuring durability.
• Fitment: Tighter lug tolerances ensure a snug fit, optimizing performance.
• Customization Opportunities: While the kit is delivered unassembled, its design allows enthusiasts to personalize their build. The aesthetic milling of the upper, adorned with Faxon’s signature “X” logo, reduces material and weight. The “X” skeletonized magwell is both a branding touch and a testament to Faxon’s dedication to weight efficiency.
• Material & Finish: Crafted from 7075-T6 Forged Aluminum and finished with Type III Hard Coat Anodizing.

The kit is also available in OD Green Cerakote, Titanium Cerakote, and Midnight Bronze for those interested in color variations. The Faxon HyperLite AR-15 Receiver Kit encapsulates a harmonious blend of design, functionality, and innovation, making it a worthy consideration for discerning builders.

Faxon Billet AR-10 Receiver Set

The Faxon Billet AR-10 Receiver Set stands as a testament to meticulous engineering and an unwavering commitment to quality. This set is tailored for discerning firearm enthusiasts seeking a comprehensive upgrade for their AR-10 rifle.

Material and Durability:

This set’s stripped upper and lower receivers are crafted from high-grade 7075-T6 aluminum billet. This choice of material ensures a balance between lightweight design and robust strength, making the set ideal for enduring rigorous use while maintaining reliability.

Design Highlights:

Faxon’s dedication to superior design is evident in several unique features:

• An integrated trigger guard enhances safety and ergonomics.
• A flared magwell facilitates quicker magazine changes, optimizing functionality during rapid-fire situations.
• A specialized tensioning screw ensures a tight fit between the upper and lower receivers, a crucial factor in boosting accuracy.

Upper Receiver Specifics:

• Made from 7075-T6 Billet Aluminum, ensuring durability without excess weight.
• Features a Type III Class 2 Hard Coat Black Anodized finish for added resilience and a polished look.
• Adheres to the DPMS High Profile standards, guaranteeing compatibility with various components.

Lower Receiver Details:

• It is also constructed from 7075-T6 Billet Aluminum, consistent with the upper receiver.
• Enhanced with features like an Extended Mag Catch Button, Threaded Bolt Catch Pin, and a Rear Takedown Detent Spring retained with a Set Screw. An Upper Receiver Tension Screw is also incorporated.
• The Right Side Bolt Release Lever, made from 4140 steel, undergoes a Blacknitride+™ treatment for increased longevity.
• While labeled with a “MULTI” caliber designation, it’s versatile enough to accommodate a range of calibers, including .308 Winchester (7.62x51mm NATO), 8.6 Blackout, .243 Winchester, 6.5 Creedmoor, .260 Remington, and .338 Federal.

Exploring the Faxon AR-15 Builder Sets

Limited Edition Faxon 9″ AR-15 Builder Set – FDE

The Faxon AR-15 Builder Set in FDE (Flat Dark Earth) is a culmination of precision engineering and innovative design. With a custom Cerakote finish, this set offers both functionality and a distinctive aesthetic.

Key Features:

• Precision Engineered Upper Receiver: Undergoes a rigorous truing process at Faxon’s facility, ensuring alignment and balance.
• Design Innovations: Features like the hollowed-out shell deflector reduce weight and add a unique visual element.
• Material and Finish: Made from 7075-T6 Forged Aluminum, with a dual finish of Type III Hard Coat Anodizing and a custom Cerakote.
• Versatility: Compatible with all intermediate cartridges, with a note on the set’s capabilities with larger bore rounds.
• Included Handguard: The set comes with the Faxon G2 Streamline Aluminum M-LOK Handguard, emphasizing ergonomic design and style.

Limited Edition Faxon 13″ AR-15 Builder Set 

This builder set showcases Faxon’s commitment to craftsmanship and design. A custom Cerakote finish in Combat Grey offers a blend of performance and aesthetics.

Key Features:

• Meticulously Crafted Upper Receiver: Trued by experts at Faxon’s factory, ensuring enhanced firearm performance.
• Design Elements: The hollowed-out shell deflector offers both aesthetic appeal and functional weight reduction.
• Material and Finish: Crafted from 7075-T6 Forged Aluminum, with a Type III Hard Coat Anodizing and a custom Cerakote finish.
• Versatility: Designed for compatibility with all intermediate cartridges, with a note on its performance with larger bore rounds.
• Included Handguard: The Faxon G2 Streamline Aluminum M-LOK Handguard complements the set.

*Also available in Charcoal Green.

Wrapping up

Choosing the right lower receiver balances objectives, budget, and familiarity with AR-15 mechanics.

• Stripped vs. Complete: For those well-versed in AR-15 mechanics, a stripped lower receiver offers a tailored, hands-on experience. On the other hand, a complete lower receiver is ideal for those seeking convenience, requiring only attachment to the upper.

Quality Over Features: While additional features can be appealing, the cornerstone of a reliable AR-15 build is a quality lower.