6.5mm Grendel
6.5mm Grendel showing variety of bullets—144 gr (9.3 g) to 90 gr (5.8 g)
Type	Rifle
Place of origin	United States
Production history
Designer	Bill Alexander and Janne Pohjoispää
Designed	2003[1]
Specifications
Parent case	.220 Russian (5.6×39mm)[2]
Case type	Rimless, bottleneck
Bullet diameter	6.71 mm (0.264 in)
Land diameter	6.50 mm (0.256 in)
Neck diameter	7.44 mm (0.293 in)
Shoulder diameter	10.87 mm (0.428 in)
Base diameter	11.15 mm (0.439 in)
Rim diameter	11.2 mm (0.44 in)
Rim thickness	1.5 mm (0.059 in)
Case length	38.7 mm (1.52 in)
Overall length	57.5 mm (2.26 in)
Case capacity	2.3 cm3 (35 gr H2O)
Rifling twist	1 in 200 mm (8 in) or 1 in 230 mm (9 in)
Primer type	Small rifle
Maximum pressure	360 MPa (52,000 psi)
Ballistic performance
Bullet mass/type Velocity Energy 90 gr (6 g) Speer TNT 2,880 ft/s (880 m/s) 1,658 ft⋅lbf (2,248 J) 108 gr (7 g) Scenar (moly)[3] 2,790 ft/s (850 m/s) 1,866 ft⋅lbf (2,530 J) 120 gr (8 g) Norma FMJBT 2,700 ft/s (820 m/s) 1,942 ft⋅lbf (2,633 J) 123 gr (8 g) Sierra Matchking 2,650 ft/s (810 m/s) 1,917 ft⋅lbf (2,599 J) 130 gr (8 g) Norma 2,510 ft/s (770 m/s) 1,818 ft⋅lbf (2,465 J)
Test barrel length: 24 inches (610 mm) Source:Alexander Arms Pressure-safe Load Data

The6.5mm Grendel (6.5×38mm) is anintermediate cartridge jointly designed byBritish-Americanarmorer Bill Alexander, competitive shooter Arne Brennan (ofHouston,Texas) andLapua ballistician Janne Pohjoispää, as a low-recoil, high-precisionrifle cartridge specifically for theAR-15 platform at medium/long range (200–800 yard). It is an improved variation of the6.5mm PPC.^[4]

The 6.5mm Grendel cartridge was first unveiled in May 2003 at theBlackwater Training Facility inNorth Carolina, where it remainedsupersonic at 1,200 yd (1,100 m) range and out-shot the7.62mm NATO with only half therecoil.^[5] Since its introduction, it has proven to be a versatile cartridge and is now expanding into other firearm design platforms includingbolt-action rifles and theKalashnikov system.^[6]

The name "Grendel" is inspired by themythical monster antagonist from theOld Englishepic poemBeowulf.^[7] It was atrademark owned by Alexander Arms (Bill Alexander's company inRadford, Virginia) and manufactured atRadford Arsenal,^[8] until legally released in 2010 forSAAMI standardization with collaboration fromHornady.^[7][9][10]

The goal of the 6.5mm Grendel design was to create an effectiveSTANAG magazine-length cartridge for theAR-15 platform that could reach 200–800 yd (180–730 m) and surpass the performance of the native5.56mm NATO/.223 Remington cartridge. Constrained by the dimension of the STANAG magazines, the Grendel's designers decided to use a shorter, larger-diametercase for higherpowder volume while allowing space for the long, streamlined, high ballistic coefficient 6.5mm (.264 cal.) bullets. Firingfactory-loadedammunition with bullets ranging from 90 to 129grains (5.8 to 8.4 g), itsmuzzle velocity varies from 2,500 ft/s (760 m/s) with 129- and 130-grain (8.4 g) bullets to 2,900 ft/s (880 m/s) with 90 gr (5.8 g) bullets (similar in velocity to a 77-grain (5.0 g) 5.56 mm round). Depending on their case material and bullet weight, 6.5mm Grendel cartridges weigh 14.7 to 17.8 grams (227 to 275 gr).

The case head diameter of the Grendel is the same as that of the5.6×39mm (.220 Russian),7.62×39mm and6.5mm PPC cases. This diameter is larger than the5.56×45mm NATO, thereby necessitating the use of a non-standard AR-15bolt. The increased case diameter results in a small reduction in the magazine ammo capacities. A 6.5mm Grendel magazine with the same dimensions as a 30-round STANAG magazine will hold 26 rounds of Grendel ammunition.

Proponents assert that the Grendel is a good "middle ground" between the 5.56×45mm NATO and the7.62×51mm NATO. It retains greaterterminal energy at extended ranges than either of these cartridges due to its higherballistic coefficient (BC).^[2] For example, the 123 gr (8.0 g) 6.5 mm Grendel bullet has morekinetic energy and betterbody armorpenetration at 1,000 m (1,100 yd) than the larger and heavier 147 gr (9.5 g) bullet of theM80 7.62mm NATO round.^{[11][12][13][14]}

In order to obtain ballistics that are 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.^[15]

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 (50.8 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.

Serbia is in process of adopting a rifle made byZastava Arms^{[16][better source needed]} in 6.5 mm Grendel caliber as main armament for its armed forces. The rifle, designatedZastava M19, is a derivative of the previous-issueM70 rifle.^[17] An American-manufactured rifle in 6.5mm Grendel caliber may also be adopted in armament for special forces units after it passes testing inTechnical Testing Center.^{[citation needed]} Three types of 6.5mm Grendel ammunition produced byPrvi Partizan ofUžice, Serbia, will be tested for use with these rifles.^{[18][19][20][21]}The French police tactical unitGIGN announced in 2025 that they are partnering with Swiss ammunition maker SwissP Defenc to produce 6.5 Grendel cartridges for the GIGN.^[22][23]

• .220 Russian (5.6×39 mm)
• .224 Valkyrie (5.6×41 mm)
• 6mm PPC
• 6mm AR, a 6 mmwildcat version which shares 6.5 Grendel's casing, but sends a (usually) lighter projectile up to 1,000 yards (900 m).
• 6mm ARC, a factory cartridge with many similarities to the 6mm AR
• 6.5×55mm Swedish
• 6.5mm Creedmoor
• 6.5×42mm, also known as 6.5 MPC (Multi Purpose Cartridge), based on a necked up .223 Remington case.^[24]
• 6.8mm Remington SPC
• 7.62×37mm Musang
• 7.62×39mm
• List of AR platform cartridges
• List of rifle cartridges
• Table of handgun and rifle cartridges

Wikimedia Commons has media related to6.5 mm Grendel.

• http://www.alexanderarms.com/

• Pistol and rifle cartridges

• Webarchive template wayback links
• Articles with short description
• Short description is different from Wikidata
• All articles lacking reliable references
• Articles lacking reliable references from March 2023
• All articles with unsourced statements
• Articles with unsourced statements from December 2018
• Commons category link from Wikidata