If you're shopping for an AR-15 complete upper for sale, you've already figured out one of the smartest ways to build or upgrade a rifle. A complete upper lets you skip the hassle of sourcing individual parts and gets you running faster — and often cheaper. But not all complete uppers are equal. This guide walks you through exactly what to look for so you don't waste money on the wrong one. What Is a Complete AR-15 Upper? A complete AR-15 upper includes everything above the lower receiver …