The 6.5 Grendel (6.5×39mm) is an intermediate cartridge jointly designed by British-American armourer Bill Alexander, competitive shooter Arne Brennan (of Houston, Texas) and Lapua ballistician Janne Pohjoispää, as a low-recoil, high-precision rifle cartridge specifically for the AR-15 platform at medium/long range (200–800 yard). It is an improved variation of the 6.5mm PPC
The 6.5 Grendel cartridge was first unveiled in May 2003 at the Blackwater Training Facility in North Carolina, where it remained supersonic at 1,200 yd (1,100 m) range and out-shot the 7.62mm NATO with only half the recoil. Since its introduction, it has proven to be a versatile cartridge and is now expanding out into other firearm design platforms including bolt-action rifles and the Kalashnikov system.
The name “Grendel” is inspired by the mythical monster antagonist from the Old English epic poem Beowulf. It was a trademark owned by Alexander Arms (Bill Alexander’s company in Radford, Virginia) and manufactured at Radford Arsenal,[until legally released in 2010 for SAAMI standardization with collaboration from Hornady.
Proponents assert that the Grendel is a good “middle ground” between the 5.56×45mm NATO and the 7.62×51mm NATO. It retains greater terminal energy at extended ranges than either of these cartridges due to its higher ballistic coefficient (BC). For example, the 123 gr (8.0 g) 6.5 mm Grendel bullet has more kinetic energy and better body armor penetration at 1,000 m (1,100 yd) than the larger and heavier 147 gr (9.5 g) bullet of the M80 7.62mm NATO round.
In order to obtain ballistics that is superior to the 7.62×51mm cartridge, a weapon with a longer barrel and firing a heavier bullet is necessary. To achieve the same results from shorter-length barrels, even heavier bullets are needed.
|Bullet velocity: 24 inch (609.6 mm) barrel|
|Bullet mass||Muzzle velocity||1,000 meter velocity|
As noted above, the Grendel case is very closely related to the .220 Russian case. In general, each additional grain of bullet weight will reduce muzzle velocity by 10.8 ft/s (6.1 m/s for each gram) and each additional inch of barrel length will increase muzzle velocity by 20 ft/s (2.4 m/s for each centimeter). Specific details are available as graphs derived from Alexander Arms’ public domain load table linked below.