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The 6.5mm Grendel (6.5×39mm) is an intermediate cartridge designed by Arne Brennan, Bill Alexander and Janne Pohjoispää as a low-recoil, high-accuracy cartridge specifically for the AR-15 platform at medium/long range (200–800 yard). It is an improved variation of the 6.5mm PPC.[4] Since its introduction, it has proven to be a versatile design and is now expanding out into other firearms including bolt-action rifles and the Kalashnikov system.[5]

6.5mm Grendel
65G 144 123 129 120 90.jpg
6.5mm Grendel showing variety of bullets—144 gr (9.3 g) to 90 gr (5.8 g)
TypeRifle
Place of originUnited States
Production history
DesignerBill Alexander and Janne Pohjoispää
Designed2003[1]
Specifications
Parent case.220 Russian[2]
Case typeRimless, bottleneck
Bullet diameter6.71 mm (0.264 in)
Neck diameter7.44 mm (0.293 in)
Shoulder diameter10.87 mm (0.428 in)
Base diameter11.15 mm (0.439 in)
Rim diameter11.2 mm (0.44 in)
Rim thickness1.5 mm (0.059 in)
Case length38.7 mm (1.52 in)
Overall length57.5 mm (2.26 in)
Case capacity2.3 cm3 (35 gr H2O)
Rifling twist1 in 8" or 1 in 9"
Primer typeSmall rifle
Maximum pressure52,000 psi (AR-15 bolt), 58,000 psi (case strength)
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[3] Scenar (moly) 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
Source(s): Alexander Arms Pressure-safe Load Data

The name "6.5mm Grendel" was a trademark owned by Alexander Arms until it was legally released to allow the cartridge to become SAAMI standardized.[6][7]

Contents

Development and historyEdit

The 6.5mm Grendel design goal was to create an effective 200–800 yard STANAG magazine-length cartridge for the AR-15 that surpassed the performance of the native 5.56mm NATO/.223 Remington cartridge. Constrained by the dimension of the magazines, the Grendel designers decided to use a shorter, larger diameter case for higher powder volume while allowing space for long, streamlined, high-ballistic coefficient (BC) bullets. Firing factory-loaded ammunition with bullets ranging from 90 to 129 grains (5.8 to 8.4 g), its muzzle 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 5.56 mm 77-grain (5.0 g) round). Depending on their case material and bullet, 6.5 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 the .220 Russian, 7.62×39mm and 6.5mm PPC cases. This diameter is larger than the 5.56×45mm NATO, thereby necessitating the use of a non-standard AR-15 bolt. The increased case diameter results in a small reduction in the capacity of standard size M16/AR-15 magazines. A Grendel magazine with the same dimensions as a 30-round STANAG magazine will hold 26 rounds of 6.5mm Grendel ammunition.

PerformanceEdit

 
C-Products 26-round Grendel Magazine

Proponents assert that the Grendel is a 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.[2] For example, the 123 gr (8.0 g) 6.5 Grendel has more energy and better armor penetration at 1,000 meters than the larger and heavier 147 gr (9.5 g) M80 7.62 NATO round.[8][9][10][11]

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.[12]

External ballisticsEdit

 
Muzzle Velocity Change with Bullet Weight
Bullet velocity: 24 inch (609.6 mm) barrel
Bullet mass Muzzle velocity 1,000 meter velocity
gr g ft/s m/s ft/s m/s
Lapua Scenar 108 7.0 2,700 820 1,166 355
Lapua Scenar 123 8.0 2,620 800 1,222 372
Lapua FMJBT 144 9.3 2,450 750 1,213 370

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.

Army and police usesEdit

Serbia is in process of adopting a rifle made by Zastava Arms [13] in 6.5 mm Grendel caliber as main armament for its armed forces. An American-manufactured rifle in 6.5mm Grendel caliber may also be adopted in armament for special forces units after it passes testing in Technical Testing Center.[citation needed] Three types of 6.5mm Grendel ammunition produced by Prvi Partizan Uzice Serbia will be tested for use with these rifles.[14][15][16][17][18]

See alsoEdit

ReferencesEdit

  1. ^ "6.5mm Grendel (internet archive copy)". Alexander Arms. Archived from the original on January 9, 2012. Retrieved 2015-10-22.
  2. ^ a b Guthrie, J (November 16, 2012). "6.5mm Grendel: The Round the Military Ought to Have". Shooting Times. Retrieved March 8, 2013.
  3. ^ "Archived copy". Archived from the original on 2016-01-08. Retrieved 2016-01-04.CS1 maint: archived copy as title (link)
  4. ^ Lewis, Jack (2007). The Gun Digest Book of Assault Weapons. Gun Digest Books. p. 77. ISBN 978-0-89689-498-3.
  5. ^ Outdoor Hub, Prototype 6.5 Grendel AK Rifle from Definitive Arms, 13 October 2015
  6. ^ "Alexander Arms Announces: The 6.5 Grendel Is An Official SAAMI Cartridge "
  7. ^ http://bulletin.accurateshooter.com/2011/10/6-5-grendel-is-approved-as-sammi-cartridge-alexander-arms-gives-up-6-5-grendel-trademark/
  8. ^ The Case for a General-Purpose Rifle and Machine Gun Cartridge (GPC) by Anthony G Williams Archived 2014-11-09 at the Wayback Machine
  9. ^ Ehrhart, Thomas P. Increasing Small Arms Lethality in Afghanistan: Taking Back the Infantry Half Kilometer. pg 37-38
  10. ^ Infantry Weapons Conference Report - SAdefensejournal.com, 9 January 2012
  11. ^ Another 7.62mm Bullet For M-16s - Strategypage.com, 8 January 2012
  12. ^ The Army’s Individual Carbine Competition: What’s Next? - SAdefensejournal.com, 24 October 2013
  13. ^ "Archived copy". Archived from the original on 2016-08-27. Retrieved 2016-07-26.CS1 maint: archived copy as title (link)
  14. ^ http://www.prvipartizan.com/search_rb.php?id=A-484
  15. ^ http://www.prvipartizan.com/search_rb.php?id=A-485
  16. ^ http://www.prvipartizan.com/search_rb.php?id=A-483
  17. ^ "Archived copy". Archived from the original on 2016-07-24. Retrieved 2016-07-26.CS1 maint: archived copy as title (link)
  18. ^ http://www.thetruthaboutguns.com/2016/10/josh-wayner/universal-service-cartridges-will-never-happen/

BibliographyEdit

  • Guns 'n' Ammo: Book of the AR-15, 2004, "The 6.5mm Grendel", David Fortier, p. 66.
  • Special Weapons for Military & Police, Annual #27 2004, "Beyond the 5.56mm NATO", Stan Crist, pp. 62–67.
  • Guns 'n' Ammo: Book of the AR-15, 2005, "6.5mm Grendel and 6.8 SPC", David Fortier, pp. 32–44.
  • Shooting Times, February 2005, "Cooking up Loads for the 6.5mm Grendel", David Fortier, pp. 52–56.
  • Shooting Illustrated, September 2005, "6.5mm Grendel and Alexander Arms", J. Guthrie, pp. 34–37, 67–69.
  • Petersen's: Rifle Shooter, March/April 2006, "Cartridge Efficiency—Why case shape matters", M. L. McPherson, pp. 22–24.
  • Shooting Times, January 2007, "Other AR Chamberings", Sidebar Article, David Fortier, p. 56.
  • Special Weapons, Semi-Annual #50 2007, "The Super Versatile AR", Charlie Cutshaw, pp. 44–45, 80–83.
  • Special Weapons, Semi-Annual #50 2007, "5.56mm NATO Alternatives", Stan Crist, pp. 52–59.
  • Shooting Times, March 2007, "Les Baer's 6.5mm Grendel AR Sets a New Standard", David Fortier, pp. 26–32.
  • Special Weapons for Military & Police #52, Spring 2007, "BETTER-IDEA 6.5mm GRENDEL," Stan Crist
  • Special Weapons for Military & Police #52, Spring 2007, "New Battlefield Requirements—New Rifles and Ammo Needed", Charlie Cutshaw

External linksEdit