Building a firearm from an 80 lower receiver gives you the flexibility to decide whether you want to assemble it as a pistol or a rifle. Both configurations offer unique advantages, and understanding the key differences is essential for creating a reliable and compliant build.
In this article, we’ll guide you through the process of converting your 80 lower into a reliable pistol or rifle, including the legal considerations, components you’ll need, and tips for optimizing performance.
What’s the Difference Between an AR Pistol and an AR Rifle?
AR Pistol:
An AR pistol is a compact firearm that uses an 80% lower but lacks a traditional rifle stock. Instead, it features a pistol brace or buffer tube and typically has a shorter barrel.
Key Features of an AR Pistol:
- Barrel length: Less than 16 inches.
- No traditional stock (uses a pistol brace or buffer tube).
- Lightweight and maneuverable.
AR Rifle:
An AR rifle has a barrel length of 16 inches or more and includes a rifle stock for shoulder-fired shooting.
Key Features of an AR Rifle:
- Barrel length: 16 inches or longer.
- Includes a fixed or adjustable rifle stock.
- Optimized for stability and accuracy at longer ranges.
Legal Considerations for Converting an 80 Lower
Before converting your 80% lower into a pistol or rifle, it’s crucial to understand the legal framework to ensure compliance with federal, state, and local laws.
Federal Regulations:
- An 80% lower receiver is not classified as a firearm until it’s completed and assembled.
- Once completed, the lower receiver must comply with federal laws regarding barrel length, overall length, and configuration.
- Rifle-to-Pistol Conversions: It is illegal to convert a rifle into a pistol. However, a completed lower that has never been assembled as a rifle can be built into a pistol.
- Short-Barreled Rifles (SBRs): Building an SBR requires approval and registration with the ATF, including a tax stamp.
State-Specific Laws:
Some states have additional restrictions on AR pistols, rifles, or certain features (e.g., barrel length, braces, magazines). Check your state’s firearm regulations before starting your build.
Components Needed for an AR Pistol or Rifle Build
Shared Components for Both Configurations:
- 80% Lower Receiver: The foundation of your build.
- Upper Receiver: Choose a compatible upper for your chosen caliber and barrel length.
- Bolt Carrier Group (BCG): Match the BCG to your caliber and gas system.
- Lower Parts Kit (LPK): Includes the trigger group, safety selector, and small components.
Unique Components for an AR Pistol Build:
- Barrel: Less than 16 inches.
- Pistol Brace or Buffer Tube: Stabilizing brace or plain buffer tube in place of a traditional stock.
- Popular Options: SB Tactical SBA3, KAK Shockwave Blade.
- Gas System: Typically uses a carbine or pistol-length gas system for reliability with short barrels.
Unique Components for an AR Rifle Build:
- Barrel: 16 inches or longer to meet rifle-length requirements.
- Stock: Fixed or adjustable rifle stock for stability and accuracy.
- Popular Options: Magpul CTR Stock, B5 Systems Bravo Stock.
- Gas System: Mid-length or rifle-length gas system for smoother cycling with longer barrels.
Steps to Convert Your 80 Lower Into a Pistol or Rifle
Step 1: Complete the Lower Receiver
Use a jig kit and appropriate tools to finish machining your 80% lower receiver, then clean and deburr it to prepare for assembly.
Step 2: Assemble the Lower
Install the lower parts kit, including the trigger group, safety selector, and magazine catch.
For a Pistol:
- Attach a buffer tube or pistol brace.
- Use a pistol buffer and spring designed for shorter setups.
For a Rifle:
- Install a rifle stock.
- Use a carbine or rifle-length buffer and spring.
Step 3: Choose and Attach the Upper Receiver
Select an upper receiver assembly that matches your desired configuration.
For a Pistol:
- Opt for a short barrel (7.5” to 12.5”).
- Ensure the upper has a pistol-length gas system for reliability.
For a Rifle:
- Use a barrel 16” or longer to meet rifle specifications.
- Mid-length or rifle-length gas systems provide smoother operation.
Step 4: Add Accessories and Optics
Customize your build with accessories to enhance its functionality and fit your intended use.
Recommended Accessories:
- Optics: Red dot for pistols; scopes for rifles.
- Grips: Ergonomic pistol grips or angled grips for better control.
- Lights and Lasers: Essential for home defense or tactical applications.
- Sling: Single-point for pistols, two-point for rifles.
Tips for Optimizing Performance
- Match Components Properly: Ensure the buffer, spring, and gas system are compatible with your chosen barrel length and configuration.
- Use Quality Parts: High-quality components improve reliability and reduce the need for troubleshooting.
- Test Functionality: After assembly, test your build at the range to ensure proper cycling and reliability.
- Fine-Tune for Recoil: Adjust the buffer weight or gas block to optimize recoil management.
Pros and Cons of Each Configuration
AR Pistol:
Pros:
- Compact and lightweight for easy maneuverability.
- Ideal for home defense or close-quarters shooting.
- Easier to transport.
Cons:
- Higher recoil due to shorter barrel and lighter weight.
- Reduced velocity and range compared to rifles.
AR Rifle:
Pros:
- Better accuracy and range with longer barrels.
- Lower recoil for more comfortable shooting.
- Greater stability with a full stock.
Cons:
- Larger and heavier, making it less maneuverable in tight spaces.
- Harder to transport discreetly.
Final Thoughts
Converting your 80% lower receiver into a pistol or rifle opens the door to endless customization possibilities, allowing you to build a firearm that fits your specific needs. Whether you prioritize compactness, long-range accuracy, or versatility, starting with an 80 lower gives you the freedom to create a reliable and compliant firearm.
Ready to start your build? Check out Thunder Guns for high-quality 80% lowers, jig kits, and all the components you need to build a reliable AR pistol or rifle. Happy building!