The 6.5mm Grendel

By Chuck Hawks

6.5mm Grendel
Illustration courtesy of Alexander Arms.

Its proponents and its opponents are comparing the 6.5mm Grendel cartridge to the 6.8mm Rem. SPC cartridge. The development of the 6.8mm SPC, a .270 caliber round, was instigated and driven by special forces shooters who wanted a more effective cartridge than the .223 for their specific combat needs. The 6.8mm SPC has also proven to be a very accurate cartridge.

The 6.5mm Grendel was designed as a cartridge for long range precision shooting with AR15 type rifles. It is basically a match cartridge, not a combat cartridge, although it may have some potential military application.

Bill Alexander of Alexander Arms and Arne Brennan (Founder of Competition Shooting Sports, Inc) developed this short, squat 6.5mm cartridge as an improved version of the earlier 6.5mm PPC, with a little help from Lapua technicians. (Lapua, the Finnish ammunition company, makes the 6.5mm Grendel brass for Alexander Arms.) Bill Alexander is an engineer with a background in defense projects. He and Arne Brennan reportedly finalized their design studies for the 6.5 Grendel cartridge in 2002. Lapua, contracted to provide the brass, added the final touches.

Alexander Arms offers rifles and factory loaded ammunition in 6.5mm Grendel caliber. Unfortunately, as far as I can determine (the Alexander Arms web site is limited in scope), these rifles are military style match/sniper rifles on the AR15 platform, which are of limited utility to mainstream hunters and shooters.

The AR15 rifle imposed certain, rather severe, constraints on the 6.5mm Grendel's design in the areas of back thrust, pressure (MAP 45,000 psi), and cartridge overall length. The new cartridge had to function safely in an action designed around, and feed through a magazine intended for, little .223 Remington cartridges. These compromises would not have been necessary had the 6.5mm Grendel been designed to function in strong, civilian rifle actions such as Browning's autoloading BAR, lever action BLR and bolt action A-Bolt II.

Freed of the constraints imposed by the AR15 rifle platform, a more versatile and effective 6.5mm cartridge design would have been possible. That was the approach taken by A-Square and Remington that resulted in the 6.5mm-08 A-Square, which was released commercially as the .260 Remington. However, that cartridge was designed with normal short action (.308 length) civilian rifles in mind, like the Browning's mentioned in the paragraph above, which are capable of routinely operating at a maximum average pressure (MAP) of 60,000 psi or more.

In the initial stages of his development process, Alexander tried a variety of calibers for his new cartridge and quickly focused on those between .257" and .284". The .264" (6.5mm) caliber was eventually chosen due to the availability of suitable bullets (in terms of weight and length) that were compatible with the restricted length of the AR15 magazine. As the model for case design, Alexander was considering the 6mm PPC, necked-up to accommodate standard .264" diameter bullets.

At about the same time that Alexander was contemplating the design of the new 6.5mm cartridge, a competitive target shooter named Arne Brennan was testing his independently developed 6.5mm PPC wildcat cartridge and rifle. Arne had ordered a custom AR15 type target rifle built for the 6.5mm PPC wildcat and this rifle was delivered late in 2000.

Arne Brennan had been shooting his custom AR15 for over a year when Lothar Walther put him in touch with Bill Alexander. From that point on, Arne Brennan and Alexander collaborated on the 6.5mm Grendel project.

A prototype 6.5mm Grendel rifle was completed and demonstrated in 2003. Lapua engineers assisted with modifications intended to optimize the case for use with 107-130 grain bullets, which included a longer shoulder and a shorter neck.

Most of the 6.5mm Grendel's case dimensions remain similar to those of the parent PPC case. The case length is 1.505", rim diameter is .442", rim thickness is .050" and head diameter is .445". The PPC's basic case shape was retained. Capacity is about 35 grains of water. Cartridge overall length is 2.255" and bullet diameter is .264" (6.5mm). MAP is about 42,000 psi. (The permissible MAP for the AR15/M16 action is only 45,000 psi, according to Alexander, so do not attempt to develop high-pressure loads for the 6.5mm Grendel cartridge.)

Loading density with the selected powder is near 100% and the claimed muzzle velocity with 120-123 grain bullets is 2600 fps. This is just about identical to the ballistics of the old 6.5x50 Jap (Arisaka) cartridge, which was introduced in 1897, with bullets of the same weight.

The intrinsic accuracy of the 6.5 Grendel is alleged to be excellent, apparently about on a par with Remington's 6.8mm SPC cartridge. It is worth remembering that U.S. soldiers in the Pacific Theatre during WW II found the accuracy of the 6.5x50 Japanese service round to be very good; far too good for comfort. The accuracy of the 6.5x55 Swedish service cartridge is legendary. Accuracy is a trait long associated with moderate 6.5mm cartridges.

Of course, the proud parents of new wildcat cartridges always claim superlative ballistics and exceptional accuracy at moderate pressure for their "children." Partisans of the 6.5mm Grendel claim superior accuracy compared to the 6.8mm SPC, but fans of the 6.8mm SPC make the same claim for their favorite in comparison to the 6.5mm Grendel. I figure that the two cartridges are probably pretty equal in terms of intrinsic accuracy, and that it is the individual shooter who makes the difference.

Arne Brennan says that he developed his original 6.5mm PPC as a dual-purpose target and hunting cartridge for AR15 style rifles. Bill Alexander did some testing along those lines. He fired 120 grain Nosler Ballistic Tip hunting bullets at a MV of 2600 fps into blocks of ballistic gelatin 300 yards distant. The results were encouraging. He reported that the Nosler bullets penetrated 18" and expanded to .51 caliber while retaining 75% of their weight. It would be interesting to find out what the results of such tests would be at the more realistic distances of 100 and 200 yards.

Unfortunately, AR15 style rifles are not legal for hunting in many parts of the world. While a 6.5mm rifle shooting a 120 grain hunting bullet at a MV of 2600 fps will certainly kill most CXP2 class game, it is hard to envision a lot of hunters choosing such a cartridge over the established 6.5x55 SE or .260 Remington, both of which will launch a 120 grain bullet at a MV of about 3000 fps and offer the increased flexibility of using bullets weighing up to 160 grains for shooting larger game.

The old 6.5x54 Mannlicher-Schoenauer cartridge, which offers a level of performance similar to the 6.5mm Grendel with light bullets, was actually designed for 140-160 grain bullets and made its reputation in Africa with the latter. The 6.5x54 was discontinued by the major American loading companies around 1940 due to lack of sales, but it is still available in North America from specialty ammunition manufacturers and in Europe. It remains considerably more versatile than the 6.5mm Grendel.

One of the real benefits of the bore size is that none of these 6.5mm cartridges kick hard enough to bother most shooters. That makes precise bullet placement easier in the field and bullet placement is the key to killing power on big game animals.

Alexander Arms offers 6.5mm Grendel ammunition factory loaded with 90 grain Speer TNT varmint bullets, Nosler 120 grain Ballistic Tip hunting bullets, and Lapua 123 grain Scenar match bullets. This ammunition is loaded using Lapua brass with an Alexander Arms headstamp and costs $20/box (20 rounds) online from Competition Shooting Sports. Alexander Arms also offers 6.5mm Grendel reloading dies made by Lee Precision ($44/set from Competition Shooting Sports).

The 120 grain Nosler Ballistic Tip bullet has a ballistic coefficient of .458 and a sectional density of .246. Here are the velocity/energy figures for that bullet in the 6.5mm Grendel: Muzzle - 2600 fps/1801 ft. lbs.; 100 yards - 2413 fps/1551 ft. lbs.; 200 yards - 2234 fps/1330 ft. lbs.; 300 yards - 2062 fps/1133 ft. lbs. At a MV of 2600 fps the trajectory of that bullet looks like this: +2.8" at 100 yards, +1.1" at 200 yards, -7.5" at 300 yards. The maximum point blank range of that load (+/- 3") is 259 yards.

Trajectory is thus the 6.5mm Grendel's primary limiting factor as a CXP2 class hunting cartridge. As a deer cartridge it is similar in capability to several late 1890's 6.5mm military cartridges (6.5x50 Jap, 6.5x52 Carcano, 6.5x54 M-S), the .250 Savage (introduced in 1915), the 7-30 Waters (developed around 1976), and the contemporary 6.8mm SPC. All of these can drive a 120 grain bullet at a MV of 2600 fps or more. Ballistically, the 6.5mm Grendel offers nothing new.

How the 6.5mm Grendel will fare against the 6.8mm SPC in the civilian market, or if either will ultimately sell well enough to become a long term success, I cannot predict. Presumably, they would need to be made available in bolt and lever action hunting rifles if they were to appeal to a broad cross section of shooters. I am not at all sure that either Alexander Arms or Remington is willing (or able) to make the attempt.

The 6.8mm SPC has the advantage of being offered by a major ammunition manufacturer with national and international distribution. It also drives its .277" bullets to somewhat higher velocity. The two cartridges may coexist in the rather esoteric sport of long range military rifle target competition, but I doubt that there is enough mainstream recreational shooter and hunter interest in cartridges of this class to sustain both in the general marketplace. There may not be enough interest to sustain either one. Note that all of the ballistically similar cartridges mentioned two paragraphs above (except the new 6.8mm SPC, which is already reported to be in trouble) are either dead or dying.

That is unfortunate. Cartridges of this class are indeed adequate for taking most CXP2 class game, such as European and North American deer. Shooters should welcome any new cartridge that combines adequate trajectory, killing power, and accuracy with low recoil.

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Copyright 2004, 2012 by Chuck Hawks. All rights reserved.