Understanding the Cornerstone: 80% Lowers
What is an 80% Lower?
At the heart of any AR-10 rifle lies the lower receiver, the serialized component considered the “firearm” under federal law. The lower receiver houses the fire control group (trigger, hammer, etc.) and the buffer tube assembly, critical for the proper function of the rifle. Unlike fully-machined “complete” lowers, 80% lowers offer an alternative path for builders seeking greater control over their firearm and, often, significant cost savings.
An 80% lower is essentially a partially completed lower receiver. It’s manufactured with a significant portion of the work already done, such as the basic shape and some of the internal features. However, the crucial steps, particularly those related to the fire control group and buffer tube, remain unfinished. This is where the “80%” designation comes from—approximately 80% of the work is done. The remaining 20% involves the machining process, which is the responsibility of the builder.
The primary advantage of utilizing an 80% lower lies in its potential for significant cost savings. Because they are not legally considered firearms in many jurisdictions until they are fully machined, they can be purchased and transferred without the usual regulations and background checks associated with complete firearms. This can translate into a considerable price difference compared to purchasing a complete lower. Furthermore, 80% lowers provide a blank canvas for customization. You have complete control over the parts used, finish, and even any engraving or modifications you desire.
However, it’s crucial to acknowledge the considerations associated with 80% lowers. Building requires some level of mechanical aptitude and the necessary tools, including a drill press, end mill, and a jig to guide the machining process. The builder assumes full responsibility for completing the lower, and this requires a commitment to safety and precision. Furthermore, understanding and adhering to local laws concerning unfinished receivers is paramount. Before embarking on this project, research and understand the specific legal requirements in your area.
Decoding the Imperfections: The World of “Blem” Lowers
What is a “Blem”?
Within the landscape of 80% lowers, another cost-saving opportunity emerges: the “blem” or blemished lower. These lowers have cosmetic imperfections that do not impact the functionality or structural integrity of the receiver. Think of them as the “slightly imperfect” versions.
What constitutes a blem? It could be a minor scratch, a surface blemish, slight discoloration, or machining imperfections that are purely cosmetic. These imperfections are usually a result of the manufacturing process and may be visible upon close inspection. Importantly, blems do not compromise the core functionality of the lower. The receiver will still accept all standard AR-10 parts and perform as designed.
The key advantage of purchasing a blem 80 AR10 Lower Blem is the price. Manufacturers often offer these lowers at a discounted rate to move them out of inventory quickly. You can often save a considerable amount, sometimes as much as 20-30% or more compared to a non-blem lower. This savings can be reinvested in other components, such as a higher-quality barrel, optic, or ammunition.
The target audience for blem lowers is primarily budget-conscious builders. These individuals prioritize performance and functionality over purely aesthetic considerations. If you’re focused on creating a reliable and accurate AR-10 without the need for flawless aesthetics, the blem option provides excellent value. For those who intend to Cerakote or otherwise refinish the lower, any minor imperfections are easily addressed.
Considerations When Choosing an 80 AR10 Lower Blem
Material Considerations
When evaluating an 80 AR10 Lower Blem, several factors deserve attention.
The materials used in the manufacture of the lower are crucial. Most 80 AR10 Lowers are constructed from high-quality aluminum alloys, typically 7075-T6 or 6061-T6. These alloys offer a balance of strength, durability, and weight. 7075-T6 is generally considered the stronger option, making it a popular choice. Ensure that the chosen lower is constructed from a reputable alloy to ensure longevity.
Finish and Appearance
The finishing process also plays a role. Manufacturers often apply hard-coat anodizing or other finishes to protect the aluminum from corrosion and wear. Blemishes can sometimes affect the finish, so it is important to inspect the lower before commencing the build. The blem may show through the finish, so consider this during purchase. The finish is often a consideration when choosing a blem, and some blems will be of little concern and others may be more noticeable.
Accuracy Concerns
Regarding accuracy, the blemishes on the receiver generally have little or no impact. The accuracy of an AR-10 is primarily determined by factors such as barrel quality, ammunition, and the shooter’s skill. The lower receiver is mainly responsible for holding the fire control components and aligning the upper and lower receivers. Minor surface imperfections do not hinder accuracy.
Manufacturer Selection
Researching reputable manufacturers is crucial. Many companies now specialize in 80% lowers, and the quality can vary. Look for manufacturers that have a proven track record and customer reviews.
Navigating the AR-10 Landscape: Crucial Compatibility Points
Understanding AR-10 Standards
The AR-10 platform is not as standardized as the AR-15. A significant portion of the parts for AR-10 style rifles are not interchangeable. Understanding this reality is essential for a successful build.
The AR-10 typically uses a larger caliber such as .308 Winchester, 6.5 Creedmoor, or other similar cartridges. This dictates the dimensions and operating characteristics of the rifle, requiring a different set of parts than the AR-15.
Compatibility Factors
Compatibility is the watchword. Different manufacturers often use varying dimensions for their components, making it crucial to thoroughly research and select compatible parts. This applies to several key areas:
- **Upper Receiver:** The upper receiver must be compatible with your chosen lower. Some lowers are designed to work specifically with DPMS-pattern or Armalite-pattern uppers. Others may offer multi-pattern compatibility.
- **Buffer Tube Assembly:** AR-10s frequently utilize longer buffer tubes and heavier buffers compared to AR-15s. Select a buffer tube and buffer spring combination that is designed for the AR-10 and compatible with the chosen caliber.
- **Bolt Carrier Group (BCG):** Ensure that the bolt carrier group is specifically designed for the .308 Winchester or the chosen caliber and is compatible with the upper receiver.
- **Magazine Compatibility:** Most AR-10s use magazines designed specifically for the platform. These are generally larger than AR-15 magazines. Choose magazines from a reputable manufacturer known for their reliability.
Prioritizing thorough research and part selection is crucial. Consulting online forums, reviewing manufacturer specifications, and reading build guides will help ensure compatibility.
Building Your AR-10: The Process Unveiled
The Machining Process
Completing an 80 AR10 Lower Blem involves machining the receiver to accept the necessary components. The level of difficulty varies, but it typically involves drilling and milling operations to create holes for the trigger pins, hammer pin, safety selector, and buffer tube.
The machining process often involves using a drill press and a milling machine. It may also involve the use of a jig, a fixture designed to hold the lower receiver and guide the cutting tools. The jig ensures that holes and features are precisely located.
Steps to Take
The process usually involves the following steps:
- **Prepare the Lower:** Secure the lower receiver in the jig.
- **Drill the Pin Holes:** Drill holes for the trigger, hammer, and safety selector.
- **Mill the Fire Control Pocket:** Remove material to create the fire control pocket, which houses the trigger, hammer, and other internal parts.
- **Drill and Tap for the Buffer Tube:** Drill and tap a hole for the buffer tube and install the buffer tube.
- **Finish and Assemble:** Deburr any sharp edges and install all components.
Numerous online resources, including videos and step-by-step guides, provide detailed instructions on completing an 80% lower.
Selecting Your Parts
When selecting parts, consider:
- Ensure the parts will fit the size of the lower receiver.
- Parts compatible with each other.
- Ensure the barrel and chamber are compatible with the bullet you plan to use.
- Ensure you get a compatible magazine for the receiver.
The Pros and Cons Examined
Advantages and Benefits
Let’s weigh the advantages and disadvantages of an 80 AR10 Lower Blem build.
- **Cost Savings:** The primary benefit is the potential for significant savings compared to purchasing a complete AR-10.
- **Customization:** The builder has complete control over the final build, selecting parts and finishes.
- **Potentially Non-Serialized:** Because the lower starts as an unfinished part, it may not be subject to the same regulations as a serialized firearm (check your local laws).
- **Performance Unaffected:** Minor cosmetic imperfections don’t impair functionality or accuracy.
Drawbacks and Disadvantages
- **Machining Required:** Builders must possess some mechanical aptitude and have the tools.
- **Cosmetic Imperfections:** Blems may have visual flaws.
- **Legal Considerations:** State and local laws on unfinished firearms must be checked and followed.
- **Potential for Compatibility Issues:** Careful planning and research are required to ensure part compatibility.
Final Thoughts: Your AR-10 Adventure Awaits
The 80 AR10 Lower Blem opens a door to building a custom AR-10 without straining your budget. You can embrace the platform’s capabilities, customize it to your liking, and save money in the process. Although some machining skills and careful part selection are necessary, the rewards are tangible: a personalized, high-performing rifle that you can be proud to own.
Remember to prioritize safety throughout the entire process. Follow all instructions carefully, wear appropriate safety equipment, and ensure that your rifle is functioning safely before firing.
This is the beginning, not the end, of the process. Research, plan, and build responsibly. Ensure that you fully understand your local and federal laws regarding the construction and ownership of firearms.
Resources
Where to Find More
- Search the web for reputable manufacturers and retailers of 80% AR-10 lowers.
- Explore online forums and build guides.
- Consult resources about firearm safety and responsible gun ownership.
By embracing the 80 AR10 Lower Blem, you open up a world of AR-10 possibilities while staying on budget. Enjoy the build, and enjoy your new AR-10!
