6.5mm Grendel: 308 Ballistics for the AR-15

When Steve Lawrence from the 6.5 Guys asked if I’d like to shoot his AR-15 chambered in 6.5mm Grendel, I said: “Absolutely!”. We were up at the “Ultimate Reloader Outpost” working on another shooting project, and had some spare time. A great opportunity to try a new AR-15 chambering!

Prior to to this experience, I knew little about the 6.5mm Grendel cartridge, and had no idea why it was developed. Steve explained that this cartridge enables an AR shooter to achieve similar ballistics to 308 Winchester from a 6.5 mm cartridge that can be utilized by rifles built on the AR-15 platform. Since the AR-15 is more compact and lighter in weight, an AR-15 in 6.5mm Grendel is an interesting alternative to the AR-10/LR308 type platforms.

When I first picked up a 6.5mm Grendel cartridge, I thought- “Wow, that’s short and compact”. It’s actually derived from the 7.62x39mm cartridge, another popular chambering for the AR-15. By necking down the 7.62x39mm to 6.5mm, more velocity is attained from a similar powder charge.


Designed in 2003, he 6.5mm Grendel is a relatively new cartridge. The “short and compact” form factor is the result of the need for more powder capacity (compared with 5.56 NATO or .223 Remington) and to allow “room” for long slender high-BC bullet profiles. At the same time, the cartridge needs to fit into AR-15 length magazines. It’s a game of trade-offs, but the 6.5mm Grendel manages these trade-offs very well.

Here are the dimensions for the 6.5mm Grendel cartridge, from the cartridge diagrams page on accurateshooter.com:


And here you can see the ballistically-similar 308 Winchester cartridge along side the 6.5mm Grendel. Different designs, different proportions, different bullet diameters, but similar trajectory. You may also notice here how Steve’s Lapua brass looks much nicer than my 7.62x51mm military brass.


Steve’s rifle means serious business. It features a 26 inch barrel, a huge muzzle brake, a two-stage trigger, and a Bushell HDMR scope held in place by a LaRue SPR quick-attach scope mount.

Here I am holding Steve’s rifle:


It’s interesting to handle rifles, examine cartridges, and to study specifications and ballistics. But the real story unfolds when you pick up the rifle and see what it (and the shooter) can do. Steve had a bunch of loaded rounds that he needed to shoot as a part of his brass preparation process, so I got to empty several magazines through the rifle. This was enough shooting to get some good mirage through the scope from the air passing over the hot barrel.

Here’s a quick video that shows me shooting Steve’s awesome rifle:

I did have one flier (first shot), but I managed to put 4 successive rounds into about 1/2″ at 100 yards at a pace of 3-4 seconds between shots. Get rid of the flier, and I’d be really happy with that.


Steve has spent quite a bit of time perfecting his loads for this cartridge and rifle. The load we were shooting is as follows:

  • Bullet: Hornady 123 grain AMAX
  • Federal small rifle match primer
  • 27.9 grains IMR 8208 XBR (Hodgdon lists 28.5 grains as max)
  • Lapua 6.5mm Grendel brass

Note: This load data is for reference only. Always cross-reference with manufacturer’s load data. Ultimate Reloader is not responsible for errors or possible issues you may have when using this load data. Use at your own risk.

Steve noted that for some reason, IMR 8208 XBR is used pretty much across the board by competitive shooters shooting 6.5mm Grendel- it seems to be just the right formulation for this unique cartridge and the peculiarities of the AR-15 platform.

It was a lot of fun to experience the 6.5mm Grendel, and I’m really impressed with Steve’s rifle and loads. It’s not hard to see why people like this cartridge. If you want to read more, check out these resources:


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One thought on “6.5mm Grendel: 308 Ballistics for the AR-15”

  1. Just getting started into reloading. I currently started shooting the Grendel and would like to know what die set I need and what brass should I get.

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