The AR-10 platform, known for its powerful .308 Winchester (7.62x51mm NATO) cartridge, offers a compelling alternative to the AR-15. Building your own AR-10 from an 80% lower receiver presents a unique opportunity for customization and cost savings, but it also requires a thorough understanding of the process and relevant regulations. This guide dives deep into the world of AR-10 80% lowers, covering everything from the basics to advanced considerations.
What is an 80% Lower Receiver?
An 80% lower receiver is a partially machined receiver blank that lacks the critical features necessary for it to be classified as a firearm under federal law. These features, often including the trigger pocket, hammer pin holes, and receiver extensions, require further machining to complete the lower. The "80%" designation signifies the percentage of machining already completed. This leaves the remaining work—often involving milling or drilling—to the builder.
AR-10 vs. AR-15 80% Lowers: Key Differences
While both AR-10 and AR-15 80% lowers share the fundamental concept of incomplete receivers, there are significant differences:
- Size and Caliber: AR-10 lowers are larger and more robust to accommodate the larger .308 Winchester cartridge. This necessitates heavier-duty machining and more substantial materials.
- Material: AR-10 lowers are typically constructed from thicker, more durable materials like billet aluminum or forged steel to handle the increased recoil and pressure.
- Complexity: Machining an AR-10 80% lower is often considered more challenging than its AR-15 counterpart due to the larger size and more intricate features. Precision is paramount to ensure functionality and safety.
- Cost: Generally, AR-10 80% lowers and the necessary tooling are more expensive.
The AR-10 80% Lower Building Process
Building an AR-10 from an 80% lower requires specialized tools and a careful approach:
1. Sourcing the 80% Lower Receiver:
Choose a reputable supplier offering high-quality AR-10 80% lowers. Verify the material and specifications to ensure compatibility with your chosen parts.
2. Acquiring Necessary Tools and Equipment:
This will include a milling machine (or jig for simpler methods), various drill bits, and possibly specialized jigs for precise hole placement. Safety equipment such as eye protection and hearing protection is crucial.
3. Machining the Lower:
Carefully follow the manufacturer's instructions and any included templates. Precise measurements and meticulous work are essential for a functional and safe firearm. Errors can lead to malfunction or even dangerous conditions.
4. Assembling the AR-10:
Once the lower receiver is fully machined, the assembly process follows standard AR-10 procedures. This involves installing the trigger group, buffer tube, and other components.
Legal Considerations and Regulations
Before undertaking any AR-10 80% lower build, it's crucial to understand the federal, state, and local laws governing the manufacture and ownership of firearms. Laws vary significantly by jurisdiction. Always comply with all applicable regulations and seek legal counsel if you have any doubts.
Choosing the Right AR-10 80% Lower: Key Factors
Several factors influence your choice of AR-10 80% lower:
- Material: Billet aluminum offers superior machining properties but can be more costly. Forged steel offers exceptional strength and durability.
- Manufacturer: Reputable manufacturers offer quality control and reliable products.
- Compatibility: Ensure the lower is compatible with your preferred parts and accessories.
Safety Precautions
Building an AR-10 from an 80% lower receiver is not a task to take lightly. Always prioritize safety:
- Use appropriate safety equipment.
- Follow manufacturer instructions precisely.
- Never handle firearms without proper training.
- Regularly inspect your firearm for wear and tear.
This comprehensive guide provides a solid foundation for understanding AR-10 80% lowers. However, remember that building a firearm is a serious undertaking that requires knowledge, skill, and a commitment to safety. Always adhere to all applicable laws and regulations.
