Introducing Hornadys' New 338 ARC!

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Hornady’s latest cartridge, the 338 Advanced Rifle Cartridge, is an interesting “AC/DC” addition to their growing ARC cartridge family. Both supersonic and subsonic loads were developed and introduced, making it an obvious competitor to both the popular 300 AAC Blackout and Q, LLC’s more recent 8.6mm Blackout. So, the immediate question is, should you consider Hornady’s new 338 ARC for your needs?

I suppose the most obvious question is, what purpose does the 338 ARC serve? Basically, it is a step-up in bore size over the 300 AAC Blackout allowing it to put a larger diameter and heavier payload on target. Unlike the 6.5mm Creedmoor-based 8.6mm Blackout (which shares the same .338-inch bore-size), Hornady’s 338 ARC fits into an AR-15. The 8.6mm Blackout, with its longer 43mm case length, requires a larger, heavier and more expensive AR-10 platform. So, in a nutshell, the 338 ARC is intended to out-perform the 300 AAC Blackout while doing it in a smaller, lighter and more compact package than the 8.6mm Blackout.

As it was intended to fit into a standard AR-15, or a micro-action bolt-gun, the 338 ARC’s parent case is the 6.5mm Grendel, the same as the 6mm ARC. So, while it doesn’t use a 5.56x45mm AR-15 bolt, Type 2 6.5mm Grendel/6mm ARC bolts are readily available. A number of companies will be offering barrels and it should feed from 6.5mm Grendel/6mm ARC magazines. This means that other than a 338 ARC barrel, bolts and magazines are not caliber specific and readily available on the commercial market. You do need a muzzle device with a large enough hole though for the .338-inch projectile. So, the 338 ARC does not require expensive proprietary parts and pieces.

Hornady is launching their new cartridge with two loads, a 307-grain SUB-X subsonic and a 175-grain hollow point supersonic in their Black line. The 307-grain SUB-X bullet is an expanding design which features a lead core, long grooves in its gilding metal jacket, and a hollow point cavity with a wide Flex Tip insert to aid expansion at low impact velocities. Advertised muzzle velocity from a 16-inch barrel is 1,050 fps. This projectile has a Sectional Density of 0.384 and a G1 Ballistic Coefficient of 0.375. The ballistic coefficient (BC) is rather low due to the relatively blunt nose. The 175-grain HP supersonic load is a bit sedate with an advertised muzzle velocity of just 2,075 fps from a 16-inch barrel. This light for caliber projectile has a sectional density (SD) of 0.219 and a G1 BC of 0.385.

When I first had a chance to examine and fire the 338 ARC in July of 2024, I immediately noticed the odd look of the loaded ammunition. The projectiles are unusually long, and extend noticeably from the case mouth. I tried to show that in the photo I snapped of the ammunition while at the range. Basically, it has a short case with a long nose. The reduced case capacity is a virtue for a subsonic cartridge, aiding both efficiency and consistency. The reduced case capacity though is, of course, a negative when it comes to supersonic loads. One interesting selling point to the 338 ARC is its advertised ability to use the same gas port setting for both supersonic and subsonic loads in an AR-15. This makes switching back and forth between ammunition types seamless.

As its main rival is the 300 AAC Blackout, let’s consider how the 338 ARC stacks up against this popular .30-caliber cartridge. In the simplest terms, the 300 AAC BLK was an attempt to put reliable subsonic and supersonic 7.62x39mm performance into an AR-15. This it succeeded in, and the cartridge became hugely popular in the US among hunters and recreational shooters. However, direct combat experience with specialized subsonic 7.62x39mm loads led the Soviet Spetsnaz to develop the 9x39mm subsonic cartridge. Basically, the accuracy and terminal performance of the 7.62x39mm subsonic ammunition was lacking. The 9x39mm with its 248- to 278-grain .364-inch projectiles put a much larger diameter and heavier payload on target, improving performance.

I mention Soviet experience with subsonic 7.62x39mm ammunition because many feel similarly about subsonic 300 AAC BLK. While it’s very quiet, the long .30-caliber projectiles at pistol velocities are difficult to get to reliably expand a significant amount. While the 338 ARC is running a similar subsonic velocity to the 300 AAC BLK, it starts out slightly larger (.33 versus .30 caliber) in diameter and heavier. The larger diameter projectile makes it easier for the Hornady engineers to design a projectile which will reliably expand at these sloth-like velocities.

What about the negatives? What are some reasons to avoid Hornady’s new 338 ARC? Some may feel Hornady didn’t bump up the volume enough with the bore size, stopping at .338-inch instead of going bigger, like the 350 Legend did. Factory ammunition will likely be expensive and if you reload, you know .338-inch projectiles are not cheap. The weight of 307-grain subsonic ammunition will be hefty as well. A 20-round magazine loaded with 307-grain 338 ARC will weigh about the same as a 40-round magazine of 150-grain 7.62x51mm NATO. Just stop and think about that.

When it comes to suppressors, you can’t simply reuse your .30-caliber can. You will need a larger .338 caliber unit, a suitable 9mm suppressor, or an even larger .45 caliber. So, that is something to consider as well. What about the supersonic load? In my opinion, the exterior ballistics of the 175-grain 338 ARC supersonic load are…unimpressive. Keep in mind the 350 Legend pushes a 180-grain bullet at a slightly faster 2,100 fps. Dropping from a 16-inch barrel to a shorter and handier barrel length, such as 12.5 inches, will further reduce that advertised 2,075 fps muzzle velocity.

On the plus side, the 338 ARC should function reliably, exhibit good accuracy, and its subsonic load should be very quiet. It will be easy to handload. Also, it doesn’t require any weird superfast barrel twists, using a one turn in eight inch twist. Terminal performance on game animals should be a noticeable step up with subsonic loads compared to 300 AAC BLK. Building a reliable AR-15 using common parts, other than the barrel, should be simple.

Hornady now has a 22 ARC, 6mm ARC and 338 ARC. Will the 338 ARC be successful? I cannot say, but it’s interesting to remember back to the 2003 SHOT Show. It was then that an engineer from Lapua, Janne Pohjoispaa, walked into Alexander Arms’ booth, unfolded a piece of paper and handed it to Bill Alexander. Drawn on it was a .220 Russian based 8.6x39mm cartridge Pohjoispaa had dubbed the .338 Lapua Tactical. Alexander replied he could build a rifle for it, but it wouldn’t be a big seller. He suggested necking the .220 Russian up to 6.5mm instead of .338, and thus the foundation for the 6.5mm Grendel was laid. All these years later, we now have a similar .338 cartridge to play with. I just wonder if a 358 ARC would have made more sense.

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