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	Arne Brennan and Janne Pohjoispaa
Designed	2003[1]
Specifications
Parent case	.220 Russian
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 (5.8 g) Speer TNT	2,880 ft/s (880 m/s)	1,658 ft·lbf (2,248 J)
120 gr (7.8 g) Norma FMJBT	2,700 ft/s (820 m/s)	1,942 ft·lbf (2,633 J)
123 gr (8.0 g) Sierra Matchking	2,650 ft/s (810 m/s)	1,917 ft·lbf (2,599 J)
130 gr (8.4 g) Norma	2,510 ft/s (770 m/s)	1,818 ft·lbf (2,465 J)
108 gr (7.0 g) Scenar (moly)	2,790 ft/s (850 m/s)	1,866 ft·lbf (2,530 J)
Test barrel length: 24 inches Source(s): Alexander Arms Pressure-safe Load Data

The 6.5mm Grendel (or 6.5×39mm) is a proprietary intermediate cartridge developed in 2002 by Arne Brennan (Founder of Competition Shooting Sports, Inc). This cartridge is an improved version of the PPC cartridge family designed by Dr. Lou Palmisano and Ferris Pindell in 1974.^[2] The first 6.5mm member of the PPC cartridge family was created in 1984 by Dr. Louis Palmisano and William Davis, Ph.D, for competition bolt action rifles and applied to the AR-15/M-16 platform in 1998 by Arne Brennan.^[3] The cartridge was designed as a low recoil, high accuracy, long-range cartridge for the AR-15 platform.

The name "6.5mm Grendel" is a trademark owned by Alexander Arms; Les Baer Custom has released a new cartridge known as the .264 LBC-AR which uses the same cartridge case, but has different chamber dimensions from those using the "6.5mm Grendel" brand.

Contents 1 Development and history 1.1 Timeline 2 Performance 2.1 External ballistics 2.2 Terminal ballistics 3 See also 4 References 5 Bibliography 6 External links

Development and history

The 6.5mm Grendel design philosophy has been summarized as "start slow and end fast". High muzzle velocities accelerate barrel wear and increase the percentage of recoil due to escaping gases but only yield good impact energy if the bullet is efficient at carrying its velocity downrange. Constrained by the length of the 5.56 mm NATO round, but wanting to launch a much heavier bullet, the Grendel designers decided to use a short, fat case for higher powder volume while saving space for long, streamlined, high ballistic coefficient (BC) bullets that give up little of their in-flight energy.^[4] Firing factory bullets 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 or siblings 7.62×39mm and the famous PPC cases, slightly larger than the 5.56×45mm NATO. This results in a minor reduction in the storage capacity of standard size M16/AR15 magazines. A Grendel magazine with the same dimensions as a STANAG 30 round 5.56 magazine will hold 26 rounds of 6.5mm ammunition.

Interestingly, the Grendel, as well as the competing 6.8 mm Remington SPC round, bear resemblance to the 50 years older .280 British, both in ballistics and tactical concept.^[5] The US Army chose the 7.62×51mm NATO over the .280 British, making it the de facto NATO standard in spite of years of British research and over the objections of NATO allies.^{[6][7][8][9][10]}

Timeline

• 1984: Dr. Louis Palmisano and WIlliam B Davis, PHD develop the 6.5mm PPC for the US Shooting Team for use in bolt action rifles in the 1986 world championships. While performance was exceptional, US Shooting Team stays with 6mm. 6.5mm PPC is shelved and never seen again, although Dr. Louis Palmisano believes the 6.5mm PPC could be a formidable competition cartridge with new sub 100 grain bullets.
• 1998: Arne Brennan conducts a theoretical study in multiple calibers and case designs to develop a new competition round for the AR15 that replicates or exceeds the performance of the 7.62 NATO (.308 Winchester). The design parameters required the cartridge, in a magazine length restricted loading (maximum of 2.255"), to be capable of propelling a projectile with a ballistic coefficient of .460-.500 at velocity of 2,650 ft/s (810 m/s) in a 20-inch (510 mm) barrel configuration. After evaluating multiple calibers and cartridges, the result of this research was the creation of a 6.5mm variant of the PPC cartridge with the chamber design optimized for the AR15 platform. The goal of the project was achieved when the completed rifle with new cartridge achieved performance of 2,650 ft/s (810 m/s) with bullets up to 128 grains.^[3]
• 2000: Arne Brennan and Dr Louis Palmisano (creator of the 22 and 6mm PPC cartridges) begin comparing data on the 6.5mm performance obtained through many thousands of rounds of shooting by Arne Brennan out to distances of 1000 yards. Dr. Palmisano and Arne continue work for many years developing specialty bullets in conjunction with JLK, Berger, and Cauteruccio Bullets.^[3][11]
• Summer 2002: Arne Brennan and Bill Alexander introduced by Lothar Walther. Arne begins to share his data and designs for the 6.5 Grendel with Bill Alexander.^[3]
• May 2003: Alexander Arms demonstrates first prototype 6.5mm Grendel weapon at Blackwater Shoot-out. The cartridge at this time is called the 26 Grendel and appears in an article in the October 2003 issue of Shotgun News.
• January 2004: First appearance of the new cartridge at the NSSF SHOT Show in Las Vegas with brass manufactured by Lapua. Building on previous work Lapua had done on a .338 Tactical prototype cartridge, Janne Pohjoispaa, R&D Engineer for Lapua and Arne Brennan, revised the cartridge by moving the shoulder forward. This change from the classic PPC design was done to improve the manufacturing process and to minimize tooling expense.
• May 2004: Competition Shooting Sports, Inc. delivers first production 6.5mm Grendel National Match and Long Range 28-inch (710 mm) barrel models.
• January 2005: Alexander Arms introduces "Grendel Designated Marksman Rifle - GDMR" model with 19.5 and 24-inch (610 mm) barrel options.
• January 2005: Competition Shooting Sports, Inc. introduces "Grendel Counter Sniper - GCS" models with 16, 18, 20 and 22-inch (560 mm) barrel options using its own .295 neck match chamber.
• May 2006: Independent ballistic gelatin testing completed for 90 gr (5.8 g) TNT, 120 grains (7.8 g) Norma, 120 gr (7.8 g) SMK, and 123 grains (8.0 g) SMK prototype.
• Aug 2006: Pressure safe loading data is published for AR platforms with 14.5- to 28.0-inch (370–710 mm) barrels.
• Aug 2006: Competition Shooting Sports, Inc. discontinues "6.5mm Grendel" branded products, and offers it's .295 neck match chamber under the name "6.5mm CSS".
• Feb 2007: Production Wolf brand ammunition becomes available.
• Nov 2009: Hornady announces 6.5mm Grendel 123gr AMax round.
• Oct 2010: 65grendel.com unofficial fan site community goes down because of an attack by hackers on the site which caused the host to discontinue service. Entire database of information was lost. Website back up and running as of November 2011.^[12]
• Jan 2010: Les Baer Custom, Inc. discontinues offering "6.5mm Grendel" branded rifles, upper assemblies and loaded ammunition, and releases the .264 LBC-AR complete with brass manufactured by Hornady and loaded ammunition from Black Hills Ammunition at the 2010 SHOT show.^[13]
• Jan 2011: SAAMI meets and does not approve the "6.5mm Grendel" cartridge submitted by Hornady because of the trademark being held by Alexander Arms.^[14]
• February 2011: Sabre Defence, 6.5mm Grendel licensee, is seized by Cadence Bank for non-payment of debts and a federal grand jury issues a 21 Count Federal Indictment against key Sabre Defence Management^[15]
• October 2011: Alexander Arms relinquished its trademark claim on 6.5mm Grendel, allowing the cartridge to become SAMMI standardized. It is expected that Hornady's previous application to SAMMI standardization 6.5mm Grendel will now be approved. This will make it possible for many companies to load ammunition or firearms in 6.5mm Grendel without the liability of an non-standardized cartridge. A press release by Wolf ammunition notes production and importation of steel cased 6.5mm Grendel, made in Russia, which should be a very low cost source of 6.5mm Grendel ammunition.

Performance

Proponents assert that the Grendel is an ideal middle ground between the 5.56 mm NATO and the 7.62 mm NATO, taking the best attributes of each. It has a flatter trajectory and retains greater terminal energy at extended ranges than either of these cartridges due to its higher ballistic coefficient.^[16] Production rifles have consistently achieved sub–minute of angle (MOA) groups at test ranges out past 600 meters.^[17] On March 6, 2006, Arne Brennan achieved a witnessed 1.198 inches (30.4 mm) group using Lapua 108 Scenar rounds at 660 yards (600 m).^[18] with a custom built bolt action rifle that had a .292 neck / 1.5 degree throat chamber (known as the 6.5mm PPCX).

External ballistics

Bullet velocity: 20 inch (508 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 PPC case. When sufficient load data was made available, a thorough study of the Grendel case, which constitutes a precisely dimensioned combustion chamber when the round is chambered, was done with the following results. 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.

Terminal ballistics

Speer technical representatives perform terminal ballistics tests in accordance with standard F.B.I. Protocols and their standard in-house procedures. They use 6 in × 6 in × 16 in (150 mm × 150 mm × 400 mm) blocks of ten percent ballistic gelatin, calibrated with a BB. These results were made public in May 2006. All tests were completed using either 14.5- or 16.0-inch (370 or 400 mm) chrome-lined rifles and shot from either 50 or 100 yards (45 or 90 m) to simulate combat conditions using short-barreled M4 format weapons. Barrel pressures were less than 345 MPa (50,000 psi). These are all production rifles and ammunition except for the prototype 123 gr (8.0 g) Sierra MatchKing (now a production bullet). In addition to the photos shown below, a 90 gr (5.8 g) TNT was tested resulting in explosive fragmentation after penetrating only 0.5 in (13 mm).

The 120-grain (7.8 g) Sierra MatchKing penetrated 3.25 inches (83 mm) before yawing and fragmenting. The 16 carbine (16 in/410 mm barrel) was used at a range of 100 yards (91 m). Impact velocity: 2,383 feet per second (726 m/s). Maximum penetration of the 120 gr (7.8 g) SMK was 19.5 inches (500 mm), maximum permanent cavity diameter was more than 6 inches (150 mm) with lesions running to gel block exterior surfaces. Depth to the maximum permanent cavity was 7.5 inches (190 mm). The bullet fragmented, with seven large pieces visible within the block. Jacket sections came to rest at 11.75 and 16.25 inches (298 mm and 413 mm), and the bullet core at 19.5 inches (500 mm).

The prototype 123 gr (8.0 g) SMK penetrated 2 inches (51 mm) before yawing and fragmenting. The 14.5 inch carbine (14.5 inches (370 mm) barrel) was used at a range of 50 yards (46 m). Impact velocity was 2,385 ft/s (727 m/s). The 123 SMK penetrated to a depth of 16.2 inches (410 mm), maximum permanent cavity diameter was more than 6 inches (150 mm) with lesions running to block exterior surfaces. Depth to the maximum permanent cavity was 7 inches (180 mm). The bullet fragmented into multiple small fragments with jacket pieces visible at 11 and 13 inches (280 and 330 mm). A small core fragment was visible at a maximum depth of 16.2 inches (410 mm).

The 120 gr (7.8 g) Norma FMJ penetrated 16.5 inches (420 mm) before veering out the side of the block and impacting the support frame. No fragmentation was evident, but the slug is believed to have tumbled at about 7 inches (180 mm) with its maximum permanent cavity at 11 inches (280 mm). Lesions of more than 6 inches (150 mm) were torn through the top and bottom block surfaces. The bullet was fired from an Alexander Arms Tactical 14.5-inch (370 mm) AR-15 rifle at a range of 50 yards (46 m) with a chronographed impact velocity of 2,405 ft/s (733 m/s).

See also

• 6.8 mm Remington SPC
• .280 British
• List of firearms
• 7.62×39mm
• 6.5×47mm Lapua
• List of handgun cartridges
• List of rifle cartridges
• List of individual weapons of the U.S. Armed Forces
• sectional density

References

Bibliography

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

External links

• Alexander Arms website
• Stanley C. Crist, "Small Arms Ammunition for the 21st Century: Hight-Performance Alternatives to the 5.56 NATO Round" (pdf), Infantry magazine, May–June 2006
• Beyond556.com Forum