Building an AR-15 platform rifle in 7.62x39mm presents a unique set of challenges and rewards compared to the more common 5.56 NATO/.223 Remington builds. This caliber offers significant advantages, including readily available ammunition, potent stopping power, and a less expensive cost per round. However, there are crucial considerations to ensure a reliable and safe build. This guide will cover the key components and decision points involved.
Understanding the 7.62x39 AR Platform
The 7.62x39mm cartridge, originating from the AK-47, has a larger diameter and significantly more recoil than the 5.56 NATO round. This necessitates modifications to standard AR-15 components to ensure proper function and longevity. Simply swapping barrels won't suffice; a comprehensive approach is needed.
Key Differences and Challenges
- Larger Cartridge: The 7.62x39mm cartridge requires a larger bolt face and magazine well compared to the 5.56 NATO.
- Increased Recoil: The substantial recoil demands heavier components and careful consideration of buffer systems.
- Magazine Compatibility: While magazines are available, finding reliable and high-capacity options can be more challenging than for 5.56 NATO.
- Headspacing: Proper headspacing is critical to ensure the cartridge reliably chambers and fires without causing damage. Improper headspacing is a leading cause of malfunctions.
Essential Components for Your 7.62x39 AR Build
Building a 7.62x39 AR requires specialized components. Using standard AR-15 parts designed for 5.56 NATO will lead to malfunctions and potential damage. Here's a breakdown of the crucial parts:
1. Lower Receiver:
The lower receiver forms the foundation of the firearm and houses the fire control group. While many standard AR-15 lowers will work, ensure it's compatible with the larger magazine well required for 7.62x39mm magazines.
2. Upper Receiver:
The upper receiver houses the bolt carrier group and barrel. Again, ensure compatibility with the 7.62x39mm cartridge. Modifications or specific upper receivers designed for this caliber are essential.
3. Bolt Carrier Group (BCG):
The BCG is specifically designed for the 7.62x39mm cartridge, featuring a larger bolt face and often heavier construction to handle the increased recoil. Using a standard 5.56 NATO BCG is unsafe and will likely cause malfunctions.
4. Barrel:
The barrel is a critical component. Choose a barrel specifically chambered for 7.62x39mm with the appropriate length and twist rate (typically 1:9.5" or 1:10"). Barrel quality significantly impacts accuracy and reliability.
5. Magazine:
Reliable 7.62x39mm magazines are crucial for smooth operation. Research different manufacturers and choose magazines known for their reliability and compatibility with your specific build.
6. Buffer System:
The buffer system (buffer tube, buffer spring, and buffer weight) needs to be adjusted to handle the increased recoil impulse. Heavier buffers are often necessary to prevent excessive recoil and potential malfunctions.
7. Gas System:
The gas system plays a vital role in cycling the action reliably. 7.62x39mm ARs often require adjustment to the gas system to ensure proper function.
Building Your 7.62x39 AR: Step-by-Step
Building an AR-15, regardless of caliber, requires meticulous attention to detail and safety. This process should only be undertaken by individuals with sufficient experience and a deep understanding of firearms assembly. Always consult qualified resources and follow all safety precautions. This is not an exhaustive guide and should not be used as the sole source for building a firearm.
Conclusion
Building a 7.62x39mm AR-15 is a rewarding project for experienced firearm builders, but it requires careful planning and the use of specific components designed for this caliber. Remember that safety is paramount, and thorough research and attention to detail are crucial throughout the entire process. If you lack the necessary experience, seek professional assistance. Always check and comply with all local, state, and federal laws and regulations regarding firearm ownership and assembly.
