Looking for the most inexpensive caliber on an AR platform to maximize fun at the range without emptying your wallet? Whether you own a standard AR-15 or are building one, rimfire options crush centerfire for high-volume plinking and practice. Here's the ultimate guide to the cheapest AR-15 calibers. Why .22 LR Is the Cheapest AR-15 Caliber for Range Days .22 LR stands out as the undisputed champion for budget-friendly AR shooting. Ammo Cost: Bulk .22 LR often runs $0.06–$0.12 per round ( …