The lower receiver is the serialized, legally-regulated component that serves as the foundation of your AR-15 build. It houses the fire control group (trigger assembly), magazine well, and provides attachment points for the stock, grip, and upper receiver. As the only part requiring an FFL transfer, choosing a quality lower receiver is crucial for your build's reliability and longevity.
Material Options
Forged Aluminum (7075-T6): The most common and trusted option, offering excellent strength-to-weight ratio. Forged lowers undergo a process that aligns the metal's grain structure, resulting in superior strength. Most mil-spec lowers use this material.
Billet Aluminum: Machined from a solid block of aluminum, billet lowers allow for more creative designs and tighter tolerances. They're often more expensive but can offer enhanced aesthetics and features like integrated trigger guards or flared magazine wells.
Polymer: Lightweight and budget-friendly, polymer lowers have improved significantly in recent years. While not as durable as aluminum under extreme conditions, quality polymer receivers from reputable manufacturers can serve well for general use.
Key Considerations
When selecting a lower receiver, pay attention to the finish quality—anodized coatings protect against corrosion and wear. Look for tight tolerances between upper and lower receivers to minimize wobble. Consider whether you want ambidextrous controls or a standard configuration. Some lowers come with enhanced features like tension screws for upper/lower fit, flared mag wells for faster reloads, or built-in trigger guards.
