This article was originally published in RifleShooter magazine and is posted here courtesy of InterMedia Outdoors


A modern universal cartridge?
A look at the history, development and evolution of the 6.5mm Grendel

By David M. Fortier


First shown in 2003, the 6.5x38mm Grendel has become very popular among shooters and hunters. Hornady’s recent introduction of 6.5mm Grendel ammunition adds fuel to the fire.

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!” I smiled. 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 like the 5.56x45mm, 5.45x39mm, 6x45mm and 7.62x39mm in the dust. Like having a Hemi under the hood, it hotrods a standard AR-15 platform allowing it to not only 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. Now Alexander is a talented engineer. Up until about twelve years ago he worked as a research and development consultant on military wares for the British Ministry of Defense. He had contracts working on everything from chain guns to PDWs. But England's draconian firearm laws eventually drove him to the US.

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 5.45x39mm M74 cartridge. Then in 2002 he began brainstorming on what to do next. Eventually the 6.5mm PPC caught his attention as it would fit his existing high strength .50 Beowulf bolt. So he machined a solid brass 6.5mm PPC dummy round to ponder over. It seemed like a fantastic cartridge which was small enough to double-stack in an AR-15 size magazine. To test the concept, he built a rifle using a free floated 24 inch stainless steel match barrel with a 1-9 inch twist. He fed it using modified USA brand 7.62x39mm magazines. Initial testing revealed the small cartridge to have excellent potential.

Now the 6.5mm PPC was hardly new. It was simply a necked up version of the incredibly successful 6mm PPC Benchrest cartridge designed by Dr. Lou Palmisano and Ferris Pindell in 1975. After experimenting with it Alexander came to the conclusion that it was a logical solution for improving both the exterior ballistics and terminal performance of an AR-15. On August 13, 2002 Alexander was introduced to Arne Brennan. An avid High Power competitor, Brennan had built an AR space gun in 6.5mm PPC. They compared notes and Brennan became a vocal supporter of Alexander’s new project. However while Brennan was solely interested in long range competition, Alexander recognized the cartridge had much more potential. The problem was the lack of cartridge cases. Both Norma and Sako had ceased production of .22 PPC and 6mm PPC cases.


A 6.5mm Grendel cartridge (at left) is pictured with one of the early preproduction 6.5mm PPC prototypes (center) initially utilized during testing, at right is a steel case 6.5x39mm.

So at the 2003 SHOT Show Alexander approached Lapua’s US importer/distributor about doing a run of .220 Russian brass reformed into 6.5mm PPC. Unfortunately, with Alexander Arms being a small fish, they had no interest. He had hit a brick wall. Then fate stepped in when a stone-faced Finn in a typically European suite appeared at his booth. Janne Pohjoispaa, an engineer from Lapua, unfolded a piece of paper and handed it to him. Drawn on it was a new cartridge concept, the 8.6x39mm 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 the foundation for the Grendel was laid.

After the show Alexander began bouncing cartridge drawings off of Pohjoispaa. Initially these were almost identical to the 6.5mm PPC. Pohjoispaa though didn’t like the long neck due to production losses. So working together the two of them evolved the design into today’s 6.5mm Grendel. 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. This served to lengthen case life in a semi-auto rifle. Alexander Arms paid for the cartridge tooling and placed an initial order for 50,000 brass cases on 24 November 2003. About this time I asked Alexander what he planned on calling the new cartridge. “.26 Grendel,” he replied. Unimpressed, I suggested 6.5mm Grendel instead. He mulled it over, and the new cartridge was christened.

The finalized 6.5x38mm Grendel cartridge has a .441 inch diameter casehead and a case length of 1.524 inches. Rim thickness, at .059 inch, is significantly thicker than a 5.56x45mm. This aids reliability. Shoulder angle is 30 degrees and a small rifle primer is utilized. Overall cartridge length runs from 2.200-2.265 inches. 80 to 144 grain projectiles may be utilized, but it performs best with bullets in the 100-123 grain range. The result is a handsome little cartridge which fits neatly into the confines dictated by the AR-15's magazine well.


While the 6.5mm Grendel is an intermediate cartridge it outperforms others in this class. L to R: 5.8x42mm Chinese, 5.45x39mm, 7.62x39mm, 5.56x45mm, 6.5mm Grendel, sectioned Grendel with 123 grain Scenar.

Due to its diminutive size one would expect the Grendel to be a purely short range number, like the visually similar 7.62x39mm. Such is not the case. Despite operating at low pressures and mid-range velocities, performance is surprising. Rather than trying to chase high velocities and dealing with high pressures, the Grendel case is designed to use very efficient projectiles. Efficient projectiles with high Ballistic Coefficients shed velocity and energy at a slower rate. Remember; it’s not the muzzle velocity which is important, but rather the retained velocity at your target.

The next task was getting the new cartridge to shoot up to its potential. The first reamer was made by JGS on 4 November 2003. It had a throat length of .163 inch and a .300 inch neck. Unfortunately, in Alexander’s words, “It shot like crap.” So the throat was shortened to .120 inch. This showed an insignificant increase in accuracy and proved very projectile sensitive. So Alexander took a page from the Swedish Mauser book.

When I asked him about this he replied, “The 6.5x55mm Swede is peculiar among all the other 6.5mms in that is has a half degree throat. 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 6.5x55mm 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. 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. We had a pressure barrel made and proceeded to test everything in sight. We concluded that the chamber design only showed a very nominal shift in pressure from the equivalent standard chamber. Everything worked extremely well.”
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.


The 6.5mm Grendel was developed by Bill Alexander, seen here engaging targets at 600 yards with a piston operated Grendel.

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. Like any new cartridge from a small company, sales started out slow. Remington releasing their 6.8x43mm SPC in the same time frame made things even more difficult. However within a couple years Wolf Performance Ammunition took note and added it to their line. This was produced specifically for them by Prvi Partizan of Serbia using brass cartridge cases. Unlike Lapua though, Prvi Partizan chose to use Large Rifle primers. Wolf’s initial load was a 123 grain Soft Point which was followed by a purpose built 120 grain Multi-Purpose Tactical (MPT). This hollow-point boat-tail load would prove very popular due to its inexpensive price and impressive terminal performance.

Since its introduction Alexander Arms has added four Grendel loads. Commercially they offer a 130 grain Swift Scirocco, 120 grain Barnes TSX and a 100 grain Berger OTM. Plus for military/LE use they developed a 125 grain AP load with a tungsten core. They claim this load will penetrate a Level III SAPI hard plate at 300 meters. This is an impressive claim for an intermediate cartridge.

The big news though has been Hornady’s recent release of 6.5mm Grendel ammunition. They developed an entirely new .264 inch diameter 123 grain A-MAX projectile specifically for this project. This is blessed with a very high .510 Ballistic Coefficient. Claimed muzzle velocity is 2,620 fps from a 24 inch barrel. Like the Lapua cases, Hornady’s brass utilizes a small rifle primer. In addition to loaded ammunition Hornady is offering dies, brass and projectiles for reloaders. They’ve also brought the cartridge to SAAMI to standardize it.


A look at some of the loads available for the Grendel, L to R: Hornady 123 grain A-MAX, Wolf 120 grain MPT, AA 100 grain Berger, AA 120 grain Nosler BT, AA 120 grain TSX, AA 129 grain SST, AA 130 grain Scirocco II, AA 110 grain Solid, AA 125 grain AP.

So what is all the fuss about? A 123 grain .26 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. The 6.5mm Grendel trounces military cartridges such as the 5.45x39mm, 5.56x45mm, 5.8x42mm Chinese, 7.62x39mm, 7.62x45mm and the old 7.92x33 Kurz. It does the same with the recently legitimized 6x45mm as well. Its chief rival is another fine cartridge, the 6.8x43mm SPC. Yet while the SPC starts out at a higher velocity, the Grendel will run it down and show it its taillights.

To demonstrate the Grendel’s accuracy I put an Alexander Arms 20 inch GDMR and 16 inch Mid-Length carbine to work. Both of these are my personal rifles which I have owned for a number of years. The GDMR started life with a Lothar Walther barrel which I binned and replaced with a fluted Satern match barrel with cut rifling and a 1-8.75 inch twist. I also replaced the original Magpul PRS stock with a collapsing Magpul ACS. The 16 inch carbine was fitted with a standard chrome-lined Government weight barrel with a 1-7.5 inch twist. Both rifles wear Alexander Arms’ new Mk 10+ G10 composite handguard which allows easy attachment/removal of rail sections.


The two Alexander Arms 6.5mm Grendels used in this article consisted of a 20 inch GDMR with fluted Satern match barrel and a 16 inch carbine with a Gov profile chrome-lined barrel. Both wear AA’s new Mk10+ handguards.

Off the bench the 20 inch GDMR posted its best groups with Hornady’s new 123 grain A-MAX load. My best five shot group came in at just .27 inch with an average of just .4 inch at 2,582 fps. Right on its heels was Alexander Arms 123 grain Scenar load which averaged .45 inch at 2,627 fps. Other top performers were Alexander Arms’ 100 grain Berger OTM which averaged .6 inch at 2,847 fps and 120 grain Nosler Ballistic Tip which averaged .8 inch at 2,600 fps. The 16 inch carbine posted its best group ever with Hornady’s 123 grain A-MAX load putting five shots into .6 inch. This load averaged .67 inch at 2,463 fps. Alexander Arms’ 100 grain Berger load also shot great averaging .8 inch at a respectable 2,723 fps. Their 123 grain Lapua also shot well averaging .9 inch at 2,523 fps.


Accuracy of both rifles is excellent. The .27 inch 5-shot group on the left was fired with the 20 inch GDMR while the .6 inch group was shot with the 16 inch using Hornady’s 123 grain A-MAX load.

Engaging targets from 3 to 300 yards with the 16 inch gun is easy. It’s light, quick to the shoulder and handles well. Smacking 20x11 inch LaRue’s 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 5.56mm 77 grain Mk262 Mod 1 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 4 inches at 600 yards. Four five shot groups with this load averaged a respectable 4.5 inches at 600 yards. I finished testing by engaging a Level IV hard plate at 100 yards with Alexander Arms 125 grain AP load. Considering this plate is rated to stop .30-’06 166 grain AP ammunition, the Grendel didn’t seem like enough gun. While the first round did not fully penetrate, a second round placed higher completely penetrated the plate. This rifle is both very smooth shooting and reliable.

My 20 inch GDMR has killed any interest I had in a semi-auto .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 7.62x51mm 175 grain M118LR sniper load. It just delivers a lighter payload on target. The 16 inch carbine is my pick for a rifle which does everything well. I’ve taken coyotes and medium game with it, used it training, dispatched pests around the farm and use it to protect the home. Dies, data and components are available and the cartridge is easy to reload. Plus cases can easily be formed from 7.62x39mm brass. Prvi Partizan was recently licensed by Alexander Arms and will be offering ammunition, including a new 110 grain FMJ load, brass and bullets under their own logo. I’m not alone in my praise for this cartridge either. It has generated interest among US and foreign military groups looking for improved terminal performance and extended reach from a 5.56x45 sized platform.


The 16 inch carbine made consistent hits on LaRue’s at 600 yards. At this distance the GDMR averaged 4.5 inches with Hornady’s new 123 grain A-MAX load.

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 5.56x45mm can offer, you’ll want to consider a 6.5mm Grendel.

Sources
Alexander Arms LLC
540-639-8356
www.alexanderarms.com

Barnes Bullets
435-856-1000
www.barnesbullets.com

Berger Bullets
714-4475456
www.bergerbullets.com

Hornady Manufacturing
800-338-3220
www.hornady.com

Lee Precision, Inc.
262-673-3075
www.leeprecision.com

Satern Custom Machining, Inc.
712-363-4991
www.saternmachining.com

Tactical Rifles
877-811-4867
www.tacticalrifles.net

TR&Z USA
203-375-8544
www.ppu-usa.com

Wolf Performance Ammunition
888-757-9653
www.wolfammo.com

good read. fortier. you info is well researched. oopc on spelling. typing w/baby in my lap.

Excellent!

Excellent article. Thank you!

Whenever my handguard comes in, I'll be finished with my 6.5 build. Upon yours and others' recommendations, I also selected the 20" Satern barrel. Picked it up a few months ago when Midway actually had them in stock* and it's been calling to me from the back of the safe ever since. I'm excited that it looks like I'm actually going to finish the rifle in the next week or two, and I can't wait to see what it'll do this Summer. Sadly, the nearest 1000-yd range is a little over 2 hours away, but I expect that it'll be well worth the drive.


If you don't mind, I do want to get your impression of the Wolf/Prvi load and its propensity to be reloaded.

I've got a box of 123 Scenars and the reloading information from AA. If I use once-fired Wolf cases, are the slightly different case dimensions and the large size primers expected to give any issues? Can I still expect ~1/2 MOA accuracy from carefully worked-up handloads, or would I be better off to just use Lapua or Hornady brass right from the get-go? Once a load is developed, can I expect it to transition relatively easily with minor re-working between the Wolf and Lapua or Hornady brass should I ever run into a glut of one or the other?

Also on the subject of reloading, I assume you would recommend sticking to benchrest primers and trimming for every loading? I'd like to use full-length resizing for reliability's sake. Have you tried neck-sizing only and is there a significant difference in accuracy? With my .223 rifles, I use full length resizing, I only trim every other reloading, and those rounds are very accurate in all of my rifles. Can I afford to be as relaxed with the 6.5 Grendel, or is there really a lot of accuracy to be gained by babying the case prep?


Not addressed in the article are POI shifts between ammunition. Obviously, some shift should be expected, but some calibers are worse than others.
Within 300 yards, .223 Rem (for example) seems to shift very minimally in my rifles between 55gr, 62gr, and my 77gr. handloads. Obviously, there's some vertical displacement given the different trajectories.
Some .30 rifles, though, and especially my K31 in 7.5 Swiss, have significant horizontal displacement. The Prvi loads shoot to roughly the same POI as GP11, but my 168SMK handloads generally impact 4-5" to the right at 100 yards. I'm still working on that load, so I hope it closes in a little bit, but the tight groups make me think I'm getting close enough that I simply need to re-zero when I want to shoot the SMKs.

I know that's a long lead-in to the question, but what kind of POI shift should I expect with the GDMR (ignoring for right now the obvious vertical shift associated with varying velocities between loads)?

Lastly, is there any particular advice you might have for the rifle's assembly process? I would assume that everything is the same as for a .223 chambered rifle, and that the standard 40-50 ft-lb torque on the barrel nut is fine, but I just wanted to check since I'm asking questions anyhow.
Oh, and I wasn't able to find any crush washers for the 9/16-24 muzzle threads. I'm planning on using a .308 crush washer and just going slow and careful to keep it centered. Should I try to get a "proper" washer or is it worth it?

Thanks in advance, I know that's a lot to chew through.



* Of note to anyone interested: I just checked and they're back in stock now after 2+ months of being out.