Building an AR-9 pistol or rifle requires a solid understanding of its components, especially the lower and upper receivers. These are the foundational parts of your firearm, and choosing the right ones is crucial for performance, reliability, and legality. This guide delves into the specifics of AR-9 lowers and uppers, helping you navigate the nuances of this popular platform.
Understanding the AR-9 Platform
The AR-9, short for ArmaLite Rifle caliber 9mm, uses the familiar AR-15 platform but chambered in 9mm. This allows for the adaptability and customization of the AR-15 system while utilizing the readily available and cost-effective 9mm ammunition. However, due to the different cartridge dimensions, several key differences exist, especially regarding the lower and upper receivers.
AR-9 Lower Receivers: The Foundation of Your Build
The lower receiver is the heart of any AR-15-style firearm, housing the fire control group, buffer tube, and magazine well. AR-9 lowers present some unique considerations:
Key Differences from AR-15 Lowers:
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Magazine Well: AR-9 lowers require a magazine well specifically designed for 9mm magazines. Standard AR-15 magazines won't fit. This is a critical element to ensure proper magazine seating and reliable feeding.
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Blower Tube: While many AR-9 lowers utilize standard AR-15 buffer tubes, some may require specialized buffer tubes or buffer tube extensions depending on the chosen buffer system and bolt carrier group.
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Compatibility: While many parts are interchangeable with AR-15 lowers, always verify compatibility with your chosen upper receiver and other components to avoid potential issues.
Choosing the Right AR-9 Lower:
Consider the following factors when selecting your lower receiver:
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Material: Most are made from aluminum, offering a balance of strength and weight. Some manufacturers offer polymer lowers, which can be lighter but may not be as durable.
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Manufacturer Reputation: Choose a reputable manufacturer with a history of producing high-quality, reliable lowers.
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Features: Some lowers offer features such as ambidextrous controls or different finishes.
AR-9 Upper Receivers: Completing the Build
The upper receiver houses the barrel, bolt carrier group, charging handle, and other essential components. AR-9 uppers also have unique characteristics compared to their AR-15 counterparts:
Key Considerations for AR-9 Uppers:
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Bolt Carrier Group (BCG): AR-9 BCGs are specifically designed for 9mm and are not interchangeable with AR-15 BCGs. Choosing a high-quality BCG is critical for reliable function.
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Barrel Length and Profile: Barrel length significantly impacts accuracy and velocity. Profile choices affect weight and handling characteristics.
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Gas System: Different gas systems exist for AR-9s, each offering its own advantages and disadvantages. Understanding the differences is crucial for optimal performance. Common options include blowback and various types of direct impingement systems.
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Handguard: The handguard protects the barrel and provides a place to mount accessories. Choose a handguard that fits your desired style and functionality.
Selecting the Right AR-9 Upper:
Consider these factors when choosing your upper receiver:
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Compatibility: Ensure the upper receiver is compatible with your chosen lower receiver and other components.
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Material and Construction: Aluminum is the most common material, offering a good combination of strength and weight. Quality construction is key for durability and reliability.
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Manufacturer Reputation: Choose a reputable manufacturer known for high-quality products.
Conclusion: Building Your AR-9
Building an AR-9 pistol or rifle can be a rewarding project, but choosing the correct lower and upper receivers is paramount. Careful consideration of the specifics outlined above will help you build a reliable and high-performing firearm. Remember always to comply with all local, state, and federal laws and regulations when building or owning firearms. This information is for educational purposes only and should not be considered legal or professional advice. Consult with relevant experts for any legal concerns or advice regarding firearm ownership and construction.
