In 2002 Bill Alexander (Alexander Arms) developed the 6.5 Grendel, based on the PPC case (which is a descendant of the .220 Russian/7.62x39 cases). It is necked to accept .264-inch bullets and has an overall cartridge length of 2.260 inches (same as the .223 Remington), making it ideal for AR rifles. Like other PPC cartridges, the Grendel has proven unusually accurate, and when stoked with high ballistic coefficient bullets is effective at ranges beyond 1000 yards. It is efficient and offers an outstanding blend of power and long-range capability when compared to other cartridges suitable for the AR-15 rifle.

The 6.5 Grendel was officially adopted by SAAMI in 2012, with maximum industry pressure limits established at 52,000 psi. Hornady factory loads have a nominal velocity of 2,590 fps with the 123- grain A-Max bullet, while the 123-grain SST is advertised at 2,620 fps.