How to Build an AR-10 in .308
Woody's answers are based on published federal and state law. Not legal advice. Consult a licensed attorney for your specific situation.
Building an AR-10 in .308 requires a larger receiver set, .308-specific barrel, appropriate bolt carrier group, and magazines designed for the cartridge. The process follows AR-15 principles but with scaled-up components.
How This Affects Your Build
The AR-10 platform predates the AR-15 and uses the same modular design philosophy scaled for full-power rifle cartridges. Unlike AR-15 builds where most components interchange freely, AR-10 parts compatibility varies between manufacturers due to different interpretations of the original specifications. Understanding these differences prevents costly compatibility issues during your build.
The Detail
Start with a matched upper and lower receiver set from the same manufacturer or verify compatibility between brands. AR-10 receivers come in two main patterns with different magazine well dimensions and bolt extension specifications. The DPMS pattern tends to be more common in the market, while the Armalite pattern follows closer to the original design dimensions.
Your barrel selection drives many other component choices. Standard .308 Winchester chambers work for most applications, while 7.62 NATO chambers offer slightly more throat length for military ammunition. The barrel extension must match your bolt, and the gas system length affects reliability. Rifle-length gas systems are most common, though mid-length systems can reduce felt recoil at the cost of potentially reduced reliability with some ammunition types.
The bolt carrier group requires careful attention to headspace and timing. AR-10 bolts use a different cam pin location and bolt extension than AR-15s. Your bolt face must properly match the barrel extension, and the gas key staking should be secure to handle the increased pressure and bolt velocity of the .308 cartridge.
Buffer system selection affects reliability significantly. AR-10s typically use heavier buffers and stiffer springs than AR-15s to control the increased bolt mass and energy. The buffer tube threads are the same, but the internal components must be sized appropriately for the larger bolt carrier mass and higher operating pressures.
Build Impact
Component compatibility between manufacturers makes AR-10 builds more complex than AR-15 projects. Stick with matched receiver sets and verify bolt/barrel compatibility before purchasing to avoid fitment issues that can derail your build timeline and budget.