Understanding the Foundation: The AR9 Kit Minus Lower
What is an AR9 Kit?
At the heart of the AR9 concept lies the AR-15 design principles adapted for pistol calibers, primarily 9mm. The AR9 offers the familiar handling and modularity of the AR-15, along with the cost-effectiveness of 9mm ammunition. These benefits are amplified by the customization potential of the platform. An AR9 kit minus the lower is a collection of parts specifically designed to work with a 9mm chambered barrel and bolt carrier group. It gives the builder the most flexible approach because it does not restrict the choice of lower receiver.
What does “Minus Lower” mean?
When a kit is advertised as “minus lower,” it means the lower receiver is not included. The lower receiver is the serialized portion of the firearm, and it’s the part you’ll purchase or register according to local laws. It is often sold this way because it allows for greater customization. You can choose the lower receiver that best suits your needs, preferences, and budget. You might prefer a certain brand, material (like aluminum or polymer), or specific features such as a last-round bolt hold-open (LRBHO). This provides a great deal of freedom in designing your AR9.
Key Components and their Function
The core functions of an AR9 rely on a set of critical parts. The *upper receiver* is the housing for the bolt carrier group, barrel, and handguard. The *barrel* guides the bullet as it exits the firearm, determining the muzzle velocity and overall accuracy. The *bolt carrier group (BCG)* is the engine of the AR9, containing the bolt, which locks into the barrel extension to create a seal for ignition. The *charging handle* is used to manually cycle the action and load the first round. The *handguard* provides a gripping surface for the support hand and protects the barrel. Finally, the *muzzle device*, such as a flash hider or compensator, controls the muzzle blast and recoil. Understanding the function of each part is essential for successful construction and reliable operation.
Making the Right Choices: Selecting AR9 Components
Selecting an AR9 Lower Receiver
The process of building an AR9 begins with choosing the right components. The lower receiver is arguably the most critical part, as it dictates the magazines your firearm will use and is the only serialized component. Many different lower receivers are available, each with its own features and price point. Consider the material, compatibility, and any desired features when choosing your lower receiver.
Choosing an AR9 Parts Kit
When selecting an AR9 kit, research and comparison are key. Reputable brands will have a reputation for quality and reliability. Read reviews and forums to learn about the experiences of other builders. Ensure the kit is specifically designed for 9mm (or the caliber you want). This will ensure proper compatibility. Pay attention to the components included in the kit, and determine whether the kit includes all the parts needed to build your upper receiver, like a barrel, BCG, and charging handle.
Optional Accessories
Beyond the core components, several accessories can improve your AR9’s performance and usability. Consider upgrading the trigger for a smoother pull and better accuracy. Optics, such as red dot sights or scopes, can significantly improve your ability to hit your target. Sights, such as backup iron sights (BUIS), are a reliable backup option. Slings can make your AR9 easier to carry. Finally, choose a magazine based on reliability, capacity, and availability.
Bringing it Together: Assembling Your AR9
Safety First
Before you begin, remember that gun safety should be paramount. Always treat every firearm as if it is loaded. Ensure the work area is clean and well-lit. Never work with a loaded firearm. When building your AR9, double-check every step. Having an understanding of the process helps immensely.
Tools Needed
Gather all the necessary tools. You’ll need a vise to hold the upper and lower receivers securely. A set of punches is essential for removing pins. A torque wrench is crucial for tightening screws to the correct specifications. Other helpful tools include a castle nut wrench, a barrel nut wrench, and a set of armorer’s blocks.
Step-by-Step Assembly Guide
1. **Installing the Barrel:** This involves attaching the barrel to the upper receiver. The barrel nut is used to secure the barrel. A barrel nut wrench is necessary to correctly tighten this nut. Following the correct torque specifications is essential for accuracy and reliability.
2. **Assembling the Upper Receiver:** Install the handguard and charging handle. The handguard is typically secured to the upper receiver, often using a proprietary system. The charging handle is inserted into the upper receiver and is responsible for cycling the action.
3. **Installing the Bolt Carrier Group:** The BCG is the heart of the AR9’s operating system. Make sure it fits properly in the upper receiver. Insert the BCG into the upper receiver after the barrel is installed.
4. **Choosing and Installing the Buffer/Spring:** The buffer and spring work to control the recoil of the firearm. It is important to select the correct buffer weight and spring for your 9mm AR9. The buffer weight and spring are crucial to proper function, reliability, and control.
5. **Attaching the Upper to the Lower:** Once the upper and lower receivers are assembled, attach them to each other using the pivot and takedown pins. This is where the building truly comes together.
6. **Optional Accessory Installation:** At this point, add any accessories, such as optics, sights, or other attachments. Install them according to the manufacturer’s instructions.
Troubleshooting Common Issues
Failure to Feed
If your AR9 fails to feed rounds, check the magazine for proper insertion and functionality. The spring could be too weak. Also, inspect the feed ramps in the upper receiver and barrel.
Failure to Extract
If the spent casings don’t eject, the extractor in the bolt carrier group might be damaged or dirty. Check the extractor and the extractor spring.
Misfeeds
Misfeeds can be caused by a variety of factors, including magazine issues, improper loading, and even ammunition problems. Identify the cause and troubleshoot.
Bolt Lock Back Issues (LRBHO)
If the bolt doesn’t lock back after the last round, there might be a problem with the LRBHO mechanism in your lower receiver or the follower in your magazine.
Legal Considerations & Safety
Federal, State, and Local Laws
It’s important to understand the legal regulations surrounding firearms, including AR9s. Regulations vary by state and local jurisdictions. Always ensure that your AR9 build complies with federal, state, and local laws. Some states have restrictions on magazine capacity, barrel length, and other features.
Safety Practices
Safety should be your primary concern, both during the building process and when using your AR9. Always treat every firearm as if it’s loaded. Make sure the firearm is pointed in a safe direction. Keep your finger off the trigger until you are ready to fire. Wear eye and ear protection. Seek training from a qualified instructor.
Maintenance and Cleaning
Cleaning Frequency
The cleaning frequency will vary depending on use. Clean the firearm after you shoot it or every few range trips.
Cleaning Procedure
Disassemble the upper receiver and clean the bolt carrier group, barrel, and other parts. Use appropriate cleaning solvents and lubricants. Proper lubrication is crucial. Use quality firearm oil on the moving parts. Consult your firearm’s manual for specific lubrication points.
Conclusion
Building an AR9 from a kit minus lower provides a satisfying experience. This process allows you to customize your firearm, understand its mechanics, and potentially save money. By following these guidelines and the proper precautions, you can build a reliable and enjoyable PCC. We covered the core components, the selection process, the assembly steps, and the maintenance.
Remember to double-check local regulations before starting your build. If you have questions or need further assistance, consult online resources and join online communities dedicated to AR9 building. Consider seeking out the expertise of experienced gunsmiths for advice. Are you ready to begin your own AR9 build?
Frequently Asked Questions
Can I use an AR-15 lower? No, AR-15 lowers are not compatible with 9mm firearms, because AR-15 lowers do not accommodate 9mm magazines.
What kind of magazines do I need? You will need magazines designed for 9mm, either Glock-style or Colt-style, depending on the lower receiver you choose.
What buffer weight should I use? The correct buffer weight varies depending on the load and the buffer spring. Generally, you will want a heavier buffer specifically designed for 9mm ARs.
What is the best barrel length? The best barrel length depends on your intended use. Shorter barrels are more compact, while longer barrels can offer increased velocity and accuracy.
Is it legal to build my own AR9? The legality depends on federal, state, and local laws. Research and comply with all regulations.
