I’ve been kind of fascinated with the various 6.5 cartridges since my teens. I remember my dad talking about how the 6.5 sits in a sweet spot as far as it’s ballistic coefficient, and how accurate the rounds could be. I have a variety of military rifles in 6.5 Japanese, 6.5 Swede and 6.5 Carcano, but kept meaning to build a modern rifle in a modern 6.5 caliber. Since I work with the AR platform so much, I kept coming back to the 6.5 Grendel, and I finally built one last fall.

The 6.5 Grendel

The 6.5 Grendel has been around for more than 20 years. It started as a proprietary round from Alexander Arms. While it offered good ballistics and worked in a standard AR-15 platform, it had something of a slow start. It wasn’t until it got its own SAMMI specs and Alexander Arms allowed other companies to use the round that it really started gaining traction. There were a variety of other 6mm based rounds out to compete with it by that point, but it still holds a solid spot on the 6mm market today.

The 6.5 Grendel uses bullet weights ranging from 90 grains to 130 grains. It’s velocity runs from around 2,880 fps at the 90-grain end to 2,510 fps at the 130-grain end. Muzzle energy is a solid 1,658 to 1,942 ft.-lbs. depending on the load. It has an effective range of 800 to 1,000 yards, depending on who you believe, and is considered suitable for predators such as coyotes and whitetail deer-sized game. It’s a middle ground round between the 5.6mm and 7.62 NATO round and in some ways outperforms both. For instance, it holds kinetic energy at longer ranges better than the 7.62 NATO due to the superior ballistic coefficient. It was also a contender for Spec Ops use competing with the 6.8mm SPC round, although neither ended up seeing any kind of official traction.

The overall length of the round is such that it fits in a regular AR-15 platform and an AR-15 magazine, but the fatter case does reduce magazine capacity. A 20 round 5.56mm holds 15 rounds of 6.5 Grendel reliably, whereas a 30-round magazine will hold around 25 rounds. Magazines are available from ASC and Duramag in 5-, 10- and 15-round capacities. ASC makes a 25-round mag, and the Duramag holds 26 rounds. Duramag also makes a curved 20-round magazine that sits in between a 5.56mm 20-round and 5.56mm 30-round mag in size. Alexander Arms of course also offers magazines in 4- and 22-round capacities. 6.5 Grendel mags will typically work with one of its competitors and the 6mm ARC as well.

Starting with KE Arms

I picked up a KE Arms KP-15 lower half in FDE this past summer. I already have a black KP-15 that I used for a lightweight 5.56 build and an OD one that I built in 7.62x39mm. I figured I’d stick to the pattern and do the FDE in yet a different caliber and thought it was finally time to do a 6.5 Grendel.

The KP-15 lowers are one-piece polymer lowers with an integrated fixed buttstock. This eliminates the common fail point on polymer lowers at the receiver extension where the buffer tube would normally screw in. The fixed stock is A1 length, which is my preference. The lower has a flared mag well and a fixed pistol grip. You do lose modularity with the KP-15 with that fixed stock and grip, but they work well for me so I don’t mind that on these builds. I like the light weight and simplicity of them. 

KE Arms sells either a stripped lower half, a complete one with a basic parts kit, or one with an upgrade parts kit. All of mine have the basic parts kit, which is basically GI spec. Since the lower half was complete, I just needed to cobble together an upper.

KM Tactical and Faxon Firearms

I started gathering parts, and I went to my usual go-to upper for modern builds, from KM Tactical. I don’t use a forward assist on a lot of my builds since I’ve never used one once in all the years that I was in the service or in police work. I will and certainly have used uppers with a FA, especially on retro builds, but I don’t go out of my way to get one on modern builds. I like the lines of the KM Tactical uppers, they’re inexpensive and have worked well on a number of builds I’ve done over the years. I picked up an FDE one to save myself from having to Moly Resin or rattle can paint the upper later.

For the barrel, I opted for a Faxon Firearms 16-inch Gunner profile with a mid-length gas system. I matched that up with a Faxon 6.5 Grendel Bolt carrier group, gas tube and low-profile gas block. Faxon makes top quality barrels, and they had everything I needed for this build.

Since I wanted to keep this build simple and lightweight, I used a GI-style barrel nut and carbine end cap and fitted the rifle with a set of Magpul MOE mid-length handguards in FDE. I finished the barrel off with a K415 H&K-style flash hider from KAK Industry. If you’ve seen my other build articles, I use a lot of KAK flash hiders and flash cans. They have a lot of options that are both practical and look good on the builds. Prices are good, too.

To finish the rifle off, I stole my Swampfox Optics Tomahawk 1-4×24 LPVO from my .308 Aero Precision SBR and added a Magpul sling. I thought the LPVO would be better suited to the 16-inch 6.5 rather than the 12-inch .308.

The last thing I did was pick up 5 15-round Duramags in FDE. I probably will get some 25- or 26-round mags eventually, but I like the low profile of the 15-round mags so I started there.

Range Time

This was my first time shooting a 6.5 Grendel out of any platform. While it’s putting out a heavier, fatter bullet at higher velocity than a 5.56mm it still proved pleasant to shoot. The KE build came in at 5.85 pounds. With the mid-length gas system though, it proved to be a smooth shooter. Although the KE Arms stock has an A1 length fixed stock, it does use a carbine buffer spring and buffer.

I picked up my 6.5 Grendel ammo from AmmoToGo. I had mostly Hornady Frontier ammo to work with for my range sessions. It’s 123-grain FMJ with a velocity of 2,580 fps, although that’s out of a longer test barrel. The load worked well in my gun with no feed or extraction issues. Sight in with my Swampfox was quick. At 25 yards my groups were basically one ragged hole, which I know is not a big deal, but I’ll take the small victories.

The other two loads I tested were the Hornady Custom 123-grain SST and the Nemo Arms 120-grain FMJ Boat Tail. Both loads performed similarly to the Hornady Frontier load that I used for the bulk of my shooting.

At 100 yards, off of the bench, I kept everything under 1.5 inches accounting for an occasional called flier. My best groups were at or just under an inch, but I was working for it. I do think with a bit more magnification than the 4x max on the LPVO, or a better trigger, I might settle down close to an inch regularly off of a rest. The Faxon barrel shoots, it’s the interface behind the trigger that’s the variable. I didn’t run the build past 100 yards before the winter weather hit, but I’m planning to take the rifle out on my club’s 300-yard range when we’re past the snow and single-digit temps. 

6.5 Wrap Up

It took me a while to finally put together a modern 6.5 rifle, but I’m pretty happy with the final results. The build is light and handy with its KP-15 lower, the Faxon Gunner profile barrel and Magpul forend. The Swampfox LPVO isn’t the lightest optic I could have used, but it works well with this configuration. Reliability and accuracy were both very good.

You can tell you’re shooting something heavier than a 5.56 with the 6.5 Grendel, but it’s still a pleasant rifle to shoot. I appreciate that the overall weight and handling is much less than my AR-10 platform guns, too. You get a round with a superior trajectory to the .308 at longer ranges and about half the recoil, too.

The 6.5 Grendel has a lot of competition these days, especially with the 6mm ARC, but it’s still a viable choice for folks who want to stick with an AR-15-size platform, but want more punch than what a 5.56mm can deliver.

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