STANAG magazine
The goal of the 6.5mm Grendel design was to create an effective STANAG magazine-length cartridge for the AR-15 platform that could reach and surpass the performance of the native 5.56mm NATO/.223 Remington cartridge. Constrained by the dimension of the STANAG magazines, the Grendel's designers decided to use a shorter, larger-diameter case for higher powder volume while allowing space for the long, streamlined, high-BC bullets. Firing factory-loaded ammunition with bullets ranging from , its muzzle velocity varies from with 129- and bullets to with bullets (similar in velocity to a 5.56 mm round). Depending on their case material and bullet weight, 6.5mm Grendel cartridges weigh .