The 6.5 Grendel is a proprietary intermediate cartridge developed in 2002 by Arne Brennan (Founder of Competition Shooting Sports, Inc). This cartridge is an improved version of the PPC

6 mm PPC

The 6 mm PPC , or 6 PPC as it is more often called, is a centerfire rifle cartridge used almost exclusively for benchrest shooting. At distances out to 300 yards, it is one of the most accurate cartridges available...

 cartridge family designed by Dr. Lou Palmisano and Ferris Pindell in 1974. The first 6.5mm member of the PPC cartridge family was created in 1984 by Dr. Louis Palmisano and William Davis, Ph.D, for competition bolt action rifles and applied to the AR-15/M-16 platform in 1998 by Arne Brennan.