6.5mm Grendel

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[2]
Case type Rimless, bottleneck
Bullet diameter 6.71 mm (0.264 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)
Rifling twist 1 in 8" or 1 in 9"
Primer type Small rifle
Ballistic performance
Bullet weight/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 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, 200-800 yard cartridge specifically for the AR-15 platform. 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 platforms including bolt-action rifles and the Kalashnikov system.

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.[5][6]

Development and history

20" Grendel Counter-Sniper

The 6.5mm Grendel design goal was to create an effective 200-800 yard AR-15 magazine-length cartridge for the AR-15 platform that surpassed the performance of the native 5.56 NATO / 223 Remington cartridge. Constrained by the length of the 5.56×45mm NATO round, 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 loaded with bullets ranging from 90 to 129 grains (5.8–8.4 g), its muzzle velocity ranges 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).

The case head diameter of the Grendel is the same as that of the parent case( the .220 Russian), the 7.62×39mm, and 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 STANAG 30-round 5.56 magazine will hold 26 rounds of 6.5mm ammunition.

Timeline

Performance

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]

While the round has impressive performance, it is not without shortfalls. Better ballistics than the 7.62×51mm cartridge require the use of a long barrel and heavy bullet. To achieve the same results from shorter length barrels, even heavier bullets are needed.[12] Because 6.5 Grendel was made to fit the dimensions of an AR-15 rifle, its performance in comparison to other 6.5 mm rounds (.260 Remington, 6.5mm Creedmoor) falls short. Grendel cases cannot hold heavy bullets (123 gr compared to around 140 gr) and rapidly drop at a range of 1,200 yd (1,097 m), where others would remain effective.[13] In comparison to the 5.56×45mm, it has a larger case diameter and reduced magazine capacity.[14]

External ballistics

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 ft/s (47 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). Therefore, a handy rule of thumb is "one inch of barrel length equals two grains of bullet weight (1 mm → 5 mg)". Specific details are available as graphs derived from Alexander Arms' public domain load table linked below.

Sporting uses

The 6.5mm Grendel is effective in the humane harvest of medium-sized game.

The cartridge developer, Bill Alexander, has been quoted as saying he was looking for a cartridge with "more legs" (i.e. longer effective range) than the .50 Beowulf so that it could be used for white tail deer hunting.[2] The round's original marketing for military and police usage created skepticism about its suitability for hunting. Despite this, there has been critical acknowledgement that it is sufficient for CXP2 class game such as deer.[15] Its manufacturer is more enthusiastic, saying that it has "flat trajectories and bullets well-suited to deer and varmints".[16] It is similar to deer cartridges such as the .30-30 Winchester, .257 Roberts and .243 Winchester but is not in the same class as the .270 Winchester or the 30-06.

See also

References

  1. "6.5mm Grendel (internet archive copy)". Alexander Arms. Archived from the original on January 9, 2012. Retrieved 2015-10-22.
  2. 1 2 3 Guthrie, J (November 16, 2012). "6.5mm Grendel: The Round the Military Ought to Have". Shooting Times. Retrieved March 8, 2013.
  3. http://www.lapua.com/en/products/reloading/bullets/centerfire-rifle-bullets/8
  4. Lewis, Jack (2007). The Gun Digest Book of Assault Weapons. Gun Digest Books. p. 77. ISBN 978-0-89689-498-3.
  5. "Alexander Arms Announces: The 6.5 Grendel Is An Official SAAMI Cartridge "
  6. http://bulletin.accurateshooter.com/2011/10/6-5-grendel-is-approved-as-sammi-cartridge-alexander-arms-gives-up-6-5-grendel-trademark/
  7. http://www.ar15.com/forums/t_3_121/649619_WOLF_STEEL_CASE_6_5MM_GRENDEL_PRODUCTION_AMMO_ARRIVED_UPDATE_with_pic_IN_OP.html
  8. The Case for a General-Purpose Rifle and Machine Gun Cartridge (GPC) by Anthony G Williams
  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. Why Most 6.5mm Cartridges are Great, but 6.5 Grendel Is Just Okay - GDIengineering.com, 14 July 2012
  14. Todd L. Parsons (October 21, 2009). "6.2mm OC" (PDF). Lead Slinger.
  15. Hawks, Chuck (2005), The 6.5mm Grendel, Guns and Shooting Online, retrieved January 31, 2013
  16. Product FAQs Q9, Alexander Arms, retrieved January 21, 2013

Bibliography

  • 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, p. 62-67.
  • Guns 'n' Ammo: Book of the AR-15, 2005, "6.5mm Grendel and 6.8 SPC," David Fortier, p. 32-44.
  • Shooting Times, February 2005, "Cooking up Loads for the 6.5mm Grendel," David Fortier, p. 52-56.
  • Shooting Illustrated, September 2005, "6.5mm Grendel and Alexander Arms," J. Guthrie, p. 34-37, 67-69.
  • Petersen's: Rifle Shooter, March/April 2006, "Cartridge Efficiency - Why case shape matters," M.L. McPherson, p. 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, p. 44-45, 80-83.
  • Special Weapons, Semi-Annual #50 2007, "5.56mm NATO Alternatives," Stan Crist, p. 52-59.
  • Shooting Times, March 2007, "Les Baer's 6.5mm Grendel AR Sets a New Standard," David Fortier, p. 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 links

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