Every few years, a new magnum darling or boutique cartridge shows up promising to make the .308 Winchester obsolete. And every few years, the .308 quietly outsells, outlasts, and outperforms the hype in the categories that actually matter to AR-10 shooters. It's not the flashiest number on paper anymore, but when you weigh ballistics, cost, availability, and sheer versatility together, .308 Winchester remains the undisputed champion of the AR-10 platform. A Cartridge Built for the Real World The …