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6.5mm Grendel AR-15 Pistol Build

If you think the 6.5mm Grendel needs a long barrel to perform well, think again!

6.5mm Grendel AR-15 Pistol Build
A Grendel pistol? Why not! A 12.5 inch barrel makes for a short quick handling package while still providing sufficient velocity for those efficient 6.5mm projectiles. (Photo by Laura A. Fortier)

There are some questions which are simply difficult to answer. How many magazines should I have for my rifle? What’s the best scope? Which handguard should I use? There’s no black and white answer to these due to the number of variables involved. What’s right for you may not fit the particular needs, or budget of someone else. It’s the same when building or buying an AR pistol and it comes time to choose the caliber. For some the answer is obvious, 5.56x45mm NATO, but there are many other great options available. These include .300 AAC Blackout, 7.62x39mm, 6.8x43mm Rem SPC, 9x19mm Parabellum and one many don’t think of for pistols, the 6.5mm Grendel.

When the 6.5mm Grendel first appeared on the market in 2004, it was viewed as a boutique cartridge from a small manufacturer, suitable only for use in long barreled target rifles. A collaboration between Bill Alexander of Alexander Arms and Janne Pohjoispaa of Lapua, the Grendel is an impressive intermediate cartridge based on the .220 Russian. Designed specifically for use in the AR-15, its main claim to fame is its ability to drive long .264-inch projectiles with a relatively high Ballistic Coefficient at moderate velocities. The use of efficient projectiles provides a level of performance far beyond what one would expect from a relative of the ballistically challenged 7.62x39mm.

6.5mm Grendel AR-15 Pistol
Bill Alexander designed the Grendel to provide a step up in performance over the 5.56mm, and it does. (Photo by Laura A. Fortier)

I shot a 300 yard iron sight prone match using preproduction 6.5mm Grendel ammunition in 2003, prior to the cartridge’s official release. This was using a 24-inch Alexander Arms competition rifle. As time went by and I became more familiar with the new cartridge, I began moving beyond paper punching and towards shorter barrels. First I dropped to a 20-inch precision rifle, and then a 16-inch carbine. It was the performance of the carbine which really opened my eyes to the cartridge’s potential. Here was a combination which could ring steel at 800 yards and flatten pigs or take whitetail in the hunting field.

About 12 years ago I had the opportunity to handle and fire a 10.5 inch gun Bill Alexander brought to an industry event. It ran flawlessly on full automatic and impressed me when I shot a group on paper with it at 500 yards. Although it performed well, I thought the short barrel length gave up just a little too much velocity. Keep in mind, I live in Kansas where shots can be long. What it did do though was spark an idea to build a very short and handy AR pistol suitable for self-protection, hunting and recreational shooting. A sort of general purpose gun if you will. My goal was to make it both short and quick handling, but I also wanted the ability to put 1,000 ft-lbs on target at 300 yards.

After crunching some numbers and estimating velocity I hypothesized my perfect barrel length for this project would be 12 inches. Unfortunately this length barrel didn’t yet exist in 6.5mm Grendel. So I called Bill Alexander and shared my thoughts with him and he agreed to build one for me. He basically cut down a 14.5 inch barrel, rethreaded the muzzle and shipped it off. What arrived was 12.5 inches, but I wasn’t going to complain. This then became my shop mule for testing.

6.5mm Grendel AR-15 Pistol
The first 12.5 inch 6.5 Grendel barrel was made by cutting down a 14.5 incher and rethreading the muzzle. This length has since become widely popular due to its performance. (Photo by Laura A. Fortier)

Performance turned out to be everything I had hoped for when I trundled it to the range. Accuracy at 100 yards from the bench was quite acceptable. It had little problem shooting into just over an inch at this distance. At 500 yards it would flatten a LaRue sniper target a 77-grain Mk262 5.56x45mm load struggled to tip over from a 20-inch rifle. With the right bullet retained energy at 300 yards was right about 1,000 ft-lbs. It was fairly short, quick handling and fast to the shoulder although recoil was noticeably heavier than for a 5.56x45mm. As to be expected, loaded Grendel magazines also weigh quite a bit more than for 5.56x45mm. Even so, the performance potential for a 12.5 inch 6.5mm Grendel seemed impressive.

6.5mm Grendel AR-15 Pistol
The 6.5mm Grendel pistol proved very quick handling, easy to carry, reliable and accurate. It’s a fun gun to shoot. (Photo by Laura A. Fortier)

Ten years ago the 6.5mm Grendel did have some glaring drawbacks though. Ammunition was not widely available, and what was on the shelves cost a pretty penny. Lapua was the primary source for brass and it was very expensive. While Prvi Partizan did also offer ammunition, their brass was soft and not of the best quality. The 6.5mm revolution had yet to begin, and so there was a limited selection of .264-inch projectiles in weights suitable for the Grendel. Reliable loading data was hard to find. Magazine selection was also limited. So, while the cartridge had potential, all was not roses.

Over time all of this changed. The 6.5mm Grendel eventually caught the eye of Hornady who presented it to SAAMI where it became an official standard. Perhaps the two things which changed the destiny of the 6.5mm Grendel the most though was the support of Wolf Performance Ammunition and the rise of the 6.5mm Creedmoor. Wolf Performance Ammunition took an early interest in the cartridge, first introducing two brass cased loads and then in 2012 a steel case load. It was Wolf’s economical 100-grain FMJ-BT steel case load which changed the landscape. As production ramped up this load became very inexpensive and widely available. Suddenly 6.5mm Grendel ammunition became similar in price to cheap steel case 7.62x39mm. When word got out on the availability of inexpensive ammunition, interest in this caliber suddenly spiked.

6.5mm Grendel AR-15 Pistol
The 6.5mm Grendel cartridge has exploded in popularity over the last few years leading to the introduction of a variety of new loads. (Photo by Laura A. Fortier)

There is little doubt that part of the 6.5mm Grendel’s recent popularity is due to the rise of the 6.5mm Creedmoor. In 2004 the 6.5mm Grendel was born into a .30-caliber world. “Americans will never embrace a 6.5mm cartridge,” was a mantra I heard over and over again back then. In its early days I often described the 6.5mm Grendel as a cartridge which bridged the gap between the 5.56x45mm and 7.62x51mm NATO. Many shooters though simply couldn’t comprehend how a cartridge similar in size and profile to the 7.62x39mm could reach effectively past 300 yards. They would look at its advertised muzzle velocity and dismiss it offhand as a short range number in a weird “European” diameter. The term “Ballistic Coefficient” was lost on many of them.

When the 6.5mm Creedmoor was introduced in 2007 it wasn’t an overnight success either. It faced the same challenges. Eventually though it’s splendid exterior ballistics finally caught the attention of American shooters. A light bulb went off and American rifleman suddenly recognized the potential of this bore-size the Europeans have been enjoying since 1891. Interest in the 6.5mm Creedmoor trickled down from long range competitors to mainstream hunters. When this happened industry reacted by introducing a whole range of modern target and hunting bullets in this bore-size, some of which were suitable for use in the 6.5mm Grendel. Many riflemen impressed by their new 6.5mm Creedmoor began looking at other 6.5mm cartridges. All of these stars lining up led to an explosion of interest in the 6.5mm Grendel over the last couple of years. Industry responded to this growing market with new companies offering 6.5mm Grendel rifles, upper receivers, barrels, magazines, ammunition and reloading components.

For those of you unfamiliar with the 6.5mm Grendel cartridge let’s take a closer look at it. The 6.5mm Grendel is based upon the .220 Russian also known as the 5.6x39mm. Developed in the Soviet Union in the 1950s as a hunting cartridge, it is itself based upon the 7.62x39mm. The .220 Russian is also the parent case of the famous .22 PPC and 6mm PPC. The 6.5mm 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 both small and large rifle primers have been utilized by different manufacturers. Overall cartridge length is 2.260 inches. 80 to 160-grain projectiles may be utilized, but it performs best with bullets in the 95-123 grain range. Bullets heavier than 130 grains tend to eat up too much case capacity and velocity tends to be on the low side. The text book 6.5mm Grendel load is a 123-grain bullet launched at 2,650 fps from a 24-inch barrel.

What is surprising about this cartridge is its performance. Due to its diminutive size one would expect the Grendel to be a purely short range number, like its visually similar older relative, the 7.62x39mm. Such is not the case. Despite operating at low pressures (52,000 PSI) and mid-range velocities, performance is surprising. Rather than trying to chase high velocities and dealing with high pressures, the 6.5mm Grendel was 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. A cartridge firing less efficient projectiles, such as the 6.8x43mm SPC, may launch them with a higher muzzle velocity. However, the more efficient projectiles of the 6.5mm Grendel often ‘run them down’ within 100 yards. The diminutive cartridge does surprisingly well at distance with a relatively flat trajectory. It also bucks the wind well. The end result is a highly flexible cartridge useful for hunting, competition shooting, recreation and self-protection.

While all this sounds good, how does the 6.5mm Grendel actually perform from a short 12.5 inch barrel? Pretty well actually. Average muzzle velocity of Alexander Arms’ 123-grain Scenar OTM is 2,330 fps. This is equal to a 7.62x39mm 123-grain load from a 16-inch AKM. Alexander Arms’ 100-grain Berger OTM averaged 2,470 fps. Wolf Performance Ammunition’s economical 100-grain FMJ-BT averaged 2,341 fps. Hornady’s 123-grain AMAX load was the slowest averaging 2,308 fps. This provides 1,455 ft-lbs of energy at the muzzle.

6.5mm Grendel AR-15 Pistol
The 6.5mm Grendel pistol turned out very well being light, quick handling and quite accurate. (Photo by Laura A. Fortier)

While 2,308 fps doesn’t sound like much, with a G1 BC of .510 this load has a retained velocity of 1,865 fps at 300 yards and still delivers an impressive 950 ft-lbs. The AMAX will reliably expand at this velocity, and actual performance on whitetail deer is very good. Proper shot placement provides quick humane kills. To put this in perspective, a 5.56x45mm pressure Hornady 75-grain OTM fired from a 20-inch rifle only delivers 736 ft-lbs at 300 yards.

Looking at Hornady’s 123-grain AMAX load a bit further, with a 200 yard zero your come-up for 300 is 1.1 Mils and at 500 yards you’ll need 3.7 Mils. Wind drift in a full value 10 mph wind at 500 yards is only 23 inches, or 1.1 Mils. So despite a moderate muzzle velocity from the short 12.5 inch barrel, this load performs surprisingly well at 500+ yards. Where a 12.5 inch Grendel really shines though is inside 200 yards. It is fast handling, easy to make rapid hits with and hits hard. Proper bullet selection provides excellent penetration of intermediate barriers as well.

6.5mm Grendel AR-15 Pistol
The 6.5 Grendel fits neatly into a standard AR-15 with the only changes being a bolt, barrel and magazine. (Photo by Laura A. Fortier)

So what do you need if you decide to build an AR pistol in 6.5mm Grendel? Only four things: a 6.5mm Grendel barrel, correct muzzle device, matching bolt and a magazine. Everything else is standard AR-15. Due to this building an AR pistol is very straightforward. Magazines are available from Alexander Arms, E-Lander and C-Products. Capacity is typically 4, 5, 10, 17 and 24 rounds. E-Lander magazines have a better reputation than C-Products so they’re what I recommend. These feature black steel bodies with anti-tilt polymer followers.

6.5mm Grendel AR-15 Pistol
An Alexander Arms 6.5 Grendel bolt was used in this build due to their high quality and proven track record. (Photo by Laura A. Fortier)

Are subsonic loads available in 6.5mm Grendel like in .300 AAC Blackout? No, at least not from the factory. However, it is possible to handload subsonic ammunition using 160-grain RN bullets, such as available from Hornady. Getting them to cycle reliably without going supersonic can be a bit tricky. I use a .30-caliber LaRue Tactical TranQilo suppressor on my 12.5 inch pistol and it works very well with standard ammunition.

6.5mm Grendel AR-15 Pistol
A Gear Head Works Tailhook arm brace was fitted which performed well. (Photo by Laura A. Fortier)

How does the 6.5mm Grendel compare to other common AR-15 cartridges? Thanks to the availability of Wolf’s 100-grain FMJ-BT load it is much less expensive to shoot than either .300 AAC Blackout or 6.8x43mm Rem SPC. As I write this 500 rounds are priced at just $134 on average. This load typically shoots about 2 inches from most rifles and performs well shooting steel out to about 450 yards. Compared to the 5.56x45mm the 6.5mm Grendel puts a larger diameter and heavier payload on target. It shoots flatter and has a higher retained velocity and energy than the 7.62x39mm and .300 AAC BLK. Performance between the 6.8x43mm Rem SPC and Grendel is fairly close.

6.5mm Grendel AR-15 Pistol
Making hits on steel at 400+ yards is not difficult even with the short barrel. (Photo by Laura A. Fortier)

I’ve been very pleased with how my 6.5mm Grendel AR pistol turned out. It’s a lot of fun to shoot, accurate, reliable and hits hard. It’s both very fun running fast engaging multiple targets at 25 yards as well as taking my time engaging steel at 800 yards. It’s easy to handload for and when I don’t feel like doing that, Wolf’s steel case load keeps me from deflating my wallet. If I want accuracy Alexander Arms, Hornady and Federal all offer high quality loads to pick from. Is it perfect? No, but it is pretty darn close to being a do-it-all gun. If you’re looking to build or buy an AR pistol or SBR, it’s definitely a caliber you should consider.

6.5mm Grendel AR-15 Pistol
Accuracy is the average of five, five-shot groups at 100 yards from a rest. Velocity is derived from a string of 10 rounds measured by a LabRadar Doppler chronograph. 1,030 feet above sea level; ambient temperature: 80 degrees F.

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