From The Hornady Web-site In Blue:
Hornady BLACK™ ammunition features versatile loads optimized for excellent performance from America’s favorite guns. Loaded with legendary Hornady® bullets, Hornady BLACK™ ammunition is designed to fit, feed and function in a variety of platforms. Direct impingement, gas piston, suppressed, unsuppressed, inertia, bolt, pump, supersonic, subsonic, rifle, mid-length, carbine or pistol – Hornady BLACK™ ammunition delivers superior performance for a variety of applications. Made in the USA.