A Monster of a Cartridge

A Monster of a Cartridge

It may be an "intermediate" round, but the 6.5mm Grendel is a fearsome performer in the AR platform.

Although a half-dozen rapid hits with Hornady 5.56mm 75-grain TAP had zero visible effect, a single 120-grain 6.5mm Grendel sent the steel plate reeling. Dropping the 16-inch Grendel from his shoulder, Jim Tarr flashed me a grin. "Man, the performance of this cartridge is so good, it should have a cape."


Without a doubt, the 6.5mm Grendel's performance is superhero-like considering its intermediate size. Exterior ballistics, retained energy and retained velocity are all a noticeable step up from established intermediate cartridges. The 6.5mm Grendel easily leaves traditional cartridges such as the 5.56x45, 5.45x39, 6x45 and 7.62x39 in the dust. Like having a Hemi under the hood, it hotrods a standard AR-15 platform, allowing it not only to hit harder but also dramatically extends its reach.

I have been shooting a 6.5mm Grendel since its debut. So with Hornady's recent introduction of 6.5mm Grendel ammunition, I thought it only fitting to take a look at its history and evolution.


I first became aware of this project in late 2002 while working on a 6.5mm project of my own. However I shelved my design after speaking with Bill Alexander, a talented engineer who worked as a research and development consultant on military wares for the British Ministry of Defense until England's draconian firearm laws eventually drove him to the United States.


Based on the .220 Russian case, the 6.5mm Grendel was developed specifically for use in AR-15s. Hornady is now loading the cartridge.

After founding Alexander Arms in 2001, he set up shop at Radford Army Arsenal. Next he designed and placed into production the .50 Beowulf and an AR-15 chambered for the Soviet 5.45x39 M74 cartridge.

Then in 2002 he began brainstorming on what to do next. Eventually the 6.5mm PPC caught his attention because it would fit his existing high-strength .50 Beowulf bolt.

To test the concept, he built a rifle using a free floated 24-inch stainless steel match barrel with a 1:9 twist. Initial testing revealed the small cartridge to have excellent potential.

The 6.5mm PPC was hardly new. It was simply a necked up version of the successful 6mm PPC Benchrest cartridge designed by Dr. Lou Palmisano and Ferris Pindell in 1975, but production of suitable cases had ceased. Alexander had hit a brick wall.

Accuracy Results | T/C Venture
6.5mm GrendelBullet Weight (gr.) Muzzle Velocity (fps)Standard Deviation Avg. Group Size (in.)
Alexander Arms GDMR
Alexander Arms Berger OTM 100 2847 6 0.6
Alexander Arms Nosler BT 120 2600 37 0.8
Hornady A-MAX 123 2,582 13 0.4
Alexander Arms Mid-Length
Alexander Arms Berger OTM 100 2,723 20 0.8
Alexander Arms Nosler BT 120 2,535 12 1.1
Hornady A-MAX 123 2,463 8 0.7
Notes: Accuracy results are averages of four five-shot groups at 100 yards off a rest. Velocities are averages of five shots measured on an Oehler 35P chronograph 12 feet from the muzzle at an ambient temperature of 90 degrees at 1,030 feet above sea level. Abbreviations: BT, ballistic tip; OTM, open-tip match.

But then fate stepped in. Lapua engineer Janne Pohjoispaa came up to Alexander at a trade show in 2003 and handed him a piece of paper. Drawn on it was a new cartridge concept, the 8.6x39 Lapua Tactical. It was basically a .220 Russian case necked up to .338, and Pohjoispaa was looking for someone to make a rifle for it. Alexander instead suggested necking the .220 Russian up to 6.5mm. When Pohjoispaa nodded, t

he foundation for the Grendel was laid.

The first step was to shorten the neck and increase case capacity. With such a relatively small case, any increase in capacity was a plus. The final change was to thicken the case neck to .012 inch to lengthen case life in a semiauto rifle.

Alexander Arms paid for the cartridge tooling and placed an initial order for 50,000 brass cases in November 2003. At about this time, I asked Alexander what he planned on calling the new cartridge. ".26 Grendel," he replied. I suggested 6.5mm Grendel instead. He mulled it over, and the cartridge was christened.

The finalized 6.5x38 Grendel cartridge has a .441-inch diameter case head and a case length of 1.524 inches. Rim thickness, at .059 inch, is significantly thicker than a 5.56x45. This aids reliability. Shoulder angle is 30 degrees, and a small rifle primer is utilized. Overall cartridge length runs from 2.200 to 2.265 inches.

The Grendel will handle 80- to 144-grain projectiles, but it performs best with bullets in the 100- to 123-grain range. The result is a handsome little cartridge that fits neatly into the confines dictated by the AR-15's magazine well.

Due to its diminutive size, one would expect the Grendel to be a purely short-range number like the visually similar 7.62x39, but despite operating at low pressures and midrange velocities, it produces excellent performance due to the bullets' high ballistic coefficients; they shed velocity and energy at a slower rate and deliver higher velocities at target distance.

The next task was getting the new cartridge to shoot. The first throat designs were found wanting, so Alexander took a page from the Swedish Mauser book.

"The 6.5x55mm Swede is peculiar among all the other 6.5mms in that it has a half-degree throat," he says. "This commences right at the end of the chamber neck. The proof is the Swede will shoot just about anything you stuff in it while maintaining a military chamber.

"However the 6.5x55 is a large case designed for single-base extruded powder. The smaller Grendel has a propensity for double-base ball type propellants. The difference is the double-base propellants are more pressure sensitive.

6.5 BC Comparison
ProjectileBullet Weight (gr.) Ballistic Coefficient
.224 inch
Sierra MatchKing 77 .362
.264 inch
Nosler Ballistic Tip 120 .458
Sierra MatchKing 123 .510
Hornady A-Max 123 .510
Hornady SST 129 .480
.277 inch
Barnes TSX 110 .323
Nosler AccuBond 110 .370
.308 inch
Sierra MatchKing 168 .462
Sierra MatchKing 175 .496

"Due to this, the half-degree throat pirated from the Mauser was not building pressure. This worried me regarding secondary detonation in extreme cold conditions, such as Alaska. So we solved this problem by designing the chamber with the back of the throat like a Swedish Mauser and the front like a stock SAMMI design. It was then dubbed a 'compound angle' throat because it has two angles, three if you count the transition from the neck to the throat."

The new chamber design proved not only very accurate but also very forgiving. This latter point is important due to the diverse weight, length and shape of available .264-inch projectiles. All production Alexander Arms 6.5mm Grendel rifles have utilized this compound angle chamber design. Delivery began in late 2004.

Initially Alexander Arms offered four loads: 90-grain TNT, 120-grain Nosler Ballistic Tip, 123-grain Lapua Scenar and 129-grain Hornady SST. Thanks to its ultra high .547 BC and excellent accuracy, the 123-grain Scenar became the standard by which all other Grendel loads are judged. Subsequent introductions include a 130-grain Swift Scirocco, 120-grain Barnes TSX and a 100-grain Berger open-tip match. There's also a military/law enforcement-only load, a 125-grain bullet with a tungsten core.

Wolf Performance also loads the round, although it uses large rifle primers. It offers a 123-grain softpoint and a 120-grain Multi-Purpose Tactical, a hollowpoint boattail.

While the 6.5mm Grendel is an intermediate cartridge it outperforms others in this class. (From l.): 5.8x42 Chinese, 5.45x39, 7.62x39, 5.56x45, 6.5mm Grendel, sectioned Grendel with 123-grain Scenar.

The big news, though, has been Hornady's recent release of 6.5mm Grendel ammunition. The company developed an entirely new 123-grain A-MAX projectile specifically for this project. This is blessed with a very high .510 BC. Claimed muzzle velocity is 2,620 fps from a 24-inch b

arrel.

Hornady's brass uses a small rifle primer, and the company is selling dies, brass and projectiles for reloaders. The cartridge is easy to reload, there's plenty of data, and you can form the cases from 7.62x39 brass.

So what is all the fuss about? A 123-grain .264 caliber slug launched at 2,523 fps from a 16-inch carbine hardly sounds remarkable. However when you crunch the numbers, you find those high BC projectiles smoke the intermediate cartridge competition downrange.

To demonstrate the Grendel's accuracy, I put my Alexander Arms 20-inch GDMR (on which I replaced the stock barrel with a fluted Satern match barrel with cut rifling and a 1:8.75 twist) and Mid-Length carbine (standard chrome-lined Government-weight barrel with a 1:7.5 inch twist) to work. Benchrest accuracy results at 100 yards are shown in the accompanying table.

Engaging targets from three to 300 yards with the 16-inch gun is easy. It's light, quick to the shoulder and handles well. Smacking 20x11-inch LaRues from 300 to 600 yards is fairly easy if you keep an eye on the conditions. The Grendel carbine flattens LaRue sniper targets that a 77-grain 5.56mm round barely rocks. Wind drift is noticeably less with the Grendel too. Muzzle jump is slightly more than a 5.56mm gun but still easy to control. Reliability is flawless.

While the 16-inch gun is accurate, the 20-inch GDMR is a laser beam. Making rapid hits on multiple targets is easy out to 600 yards. At one point I fired three rounds of Hornady's 123-grain A-Max load in four seconds. All three dropped into just four inches at 600 yards. Four five-shot groups with this load averaged a respectable 4.5 inches at 600 yards.

My 20-inch GDMR has killed any interest I had in a semiauto .308 precision rifle. It's lighter, handier, recoils less, uses common AR-15 parts, and the ammo weighs less. Plus it will drive a 123-grain Scenar flatter and with less wind drift than a 7.62x51 175-grain M118LR sniper load. It just delivers a lighter payload on target.

The 16-inch carbine is my pick for a rifle that does everything well. I've taken farm pests, coyotes and medium game with it and used it training.

I'm not alone in my praise for this cartridge. It has generated interest among U.S. and foreign military groups looking for improved terminal performance and extended reach from a 5.56x45-size platform.

Is the Grendel perfect? No, but considering it's an intermediate cartridge intended for use in an AR-15 platform, it performs extremely well. It will never be a magnum, so if you need more oomph I suggest stepping up to a .260 Rem. However, if you're looking for an AR-15 with more performance than a 5.56x45 can offer, you'll want to consider a 6.5mm Grendel.

Cartridge Comparison
5.56x45 75-gr.OTM 6.5 Grendel 123-gr.Scenar6.8mm SPC 110-gr. BarnesTSX 7.62x39 123-gr. FMJ (in.)
Muzzle
Velocity (fps) 2,750 2,523 2,650 2,330
Energy (ft.-lbs.) 1,259 1,738 1,715 1,482
100 Yards
Velocity (fps) 2,523 2,366 2,376 2,042
Energy (ft.-lbs.) 1,060 1,528 1,378 1,139
Drop (in.) 0 0 0 0
Drift (in.) 0.8 0.6 1.1 1.5
200 Yards
Velocity (fps) 2,307 2,215 2,118 1,776
Energy 886 1,339 1,096 862
Drop -3.9 -4.7 -4.7 -6.8
Drift 3.5 2.8 4.7 6.6
300 Yards
Velocity 2,102 2,069 1,878 1,537
Energy 736 1,169 861 645
Drop -14 -16 -17 -24
Drift 8.2 6.5 11.3 15.9
400 Yards
Velocity 1,908 1,929 1,656 1,332
Energy 606 1,016 670 484
Drop -32 -36 -39 -57
Drift 15 12 21 30
500 Yards
Velocity 1,726 1,795 1,457 1,169
Energy 496 880 519 373
Drop -60 -65 -74 -110
Drift 25.3 19.5 35.4 49.9
600 Yards
Velocity 1,558 1,668 1,287 1,056
Energy 404 760 404 304
Drop -100 -105 -126 -187
Drift 38.3 29 54 74.9

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