Hornady's New 338 ARC: A CLOSE-RANGE SLEDGEHAMMER

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There’s a new ARC cartridge from Hornady, and it could very possibly be the best subsonic cartridge ever. For anyone who doesn’t already know it, ARC stands for Advanced Rifle Cartridge, and the new .338 version joins the established and popular 6mm ARC and the relatively new .22 ARC. What drew my attention to this new one was a comment Hornady’s Seth Swerczek made during an interview with Gun Talk’s Tom Gresham. Swerczek said, “If you feel comfortable hunting with a .44 Magnum, any animal, and at any distance you would shoot a .44 Magnum, that .338 ARC with its 307-grain SUB-X bullet can do.”

Prior to hearing that statement, I wondered whether the .338 ARC was simply a response to the 8.6 Blackout, which is a cartridge that as a Westerner who hunts wide-open country and plays tactical man not at all, I’ve found little practical use for. I was wrong, on several counts. First, according to Hornady’s ballistician Jayden Quinlan, the .338 ARC concept has been in research and development since 2017, which predates the 8.6 Blackout. Second, the .338 ARC is anything but a “me too” cartridge; it’s the epitome of subsonic perfection. In other words, it provides best-in-class subsonic authority, efficiency, versatility, and accuracy.

Shooting subsonic was the realm of relatively few shooters until recently. Either you were a military or LE operator with a need for ultimate discretion or a hunter who shot a lot of game up close (nighttime feral hog management or urban whitetail population management, for example) and needed to do so as quietly as possible. Those covered the needs. A more recently developed—and certainly the largest—demographic of subsonic shooters is those who simply want to shoot very quiet cartridges in suppressed firearms. And that, my friends, is just as valid as an actual need.

For the most part, this report will focus on what the .338 ARC is and what it does best. But because it will inevitably be compared to the 8.6 Blackout, I’ll pit the two against each other just a bit. Here’s the first profound difference: The .338 ARC fits perfectly into standard, sleek AR-15 rifles, while the 8.6 Blackout requires an AR-10 or at least a small-frame/AR-10 hybrid receiver.

The Technology

To make the .338 ARC ultimately efficient with heavy bullets at subsonic velocity, Hornady engineered it with a relatively small-capacity case. Its parent case is the ARC case, which is derived from the 6.5 Grendel case. The Grendel case, in turn, is rooted way back in the .220 Russian.

Case head diameter is 0.441 inch; overall case length is 1.3 inches. A 30-degree shoulder provides a small but precise angle for the cartridge to headspace against. Neck length is 0.369 inch, so it’s slightly greater than the full-caliber length many experts suggest is necessary to securely hold a bullet well-aligned and concentric.

Recommended primer size is Small Rifle Magnum. You might think that it should be capped with Large Rifle primers since it’s .338 caliber, but propellant capacity, not bore diameter, dictates primer suitability. With optimal propellants, the .338 ARC uses just 9 to 10 grains of powder. Hornady submitted the .338 ARC to SAAMI with a rifling twist rate of 1:8, which is nearly three times slower than the eyebrow-raising 1:3 twist rate of the 8.6 Blackout. I’ll delve more into why shortly.

To perform in the subsonic realm, the top velocity limit is 1,100 fps. The speed of sound is just north of that, depending on your altitude and temperature. The .338 ARC’s flagship factory load pushes a 307-grain SUB-X bullet at 1,050 fps, safely under the transonic threshold. Muzzle energy is 752 ft-lbs. Bullet drop and wind deflection at distance? Those are the wrong questions to ask about the .338 ARC. It’s a close-range sledgehammer that’s nearly silent, not a far-reaching precision cartridge.

That 307-grain SUB-X is not your average heavy-for-caliber projectile drafted into service in a subsonic cartridge. It’s designed for the .338 ARC from the ground up, utilizing every benefit of Hornady’s vast R&D capabilities. “We know what knobs to turn as far as bullet design goes, to make it work,” said Swerczek. “But it still takes a significant amount of testing in ballistics gelatin to really make it perfect, and our R&D team did a wonderful job with it.”

Designed to expand from 1.5 to two times original diameter down to very slow impact speeds—slower than any hunter will ever need—the 307-grain SUB-X maximizes energy deposit on impact. It leans heavily on bullet weight, and its larger-than-average 0.338-inch diameter to achieve that. According to Hornady, it’s the ideal balance of bullet diameter and weight to provide best-in-class wallop at a very comfortable price in recoil. “The 307-grain SUB-X in the .338 ARC is really the pinnacle of performance in a subsonic bullet,” said Quinlan.

The other initial factory load is supersonic, and it pushes Hornady’s 175-grain HP Match bullet at 2,075 fps. Its muzzle energy is substantially higher at 1,673 ft-lbs. This round is faster than the speed of sound and, as a result, is much louder than the 307-grain subsonic load. On the plus side, it shoots fast enough to be useful farther out. When zeroed at 200 yards, the 175-grain HP Match bullet arches 4.2 inches high at 100 yards, then drops 16.3 inches low at 300 yards.

That’s not flat by any means, but if you have a good holdover reticle or dial-up turret, you can learn to compensate for that trajectory and make reliable hits on steel targets and game like feral hogs.

One benefit of the .338 ARC when compared to the 8.6 Blackout is that the ARC uses a reasonable rifling twist rate of one turn in every eight inches. That makes the ARC compatible with all common 0.338-inch-diameter bullets designed for cartridges like the .338 Federal, the .338 Win. Mag., the 33 Nosler, the .338 Norma, the .338 RUM, and the .340 Weatherby. For people handloading the .338 ARC, the bullet world is the reloader’s oyster.

Comparatively, the 8.6 Blackout’s extremely fast 1:3 rifling twist rate requires special bullets. Rotational velocity is extreme and, at least in supersonic loadings, often causes conventional cup-and-core hunting and target bullets to rupture and fly apart as soon as they exit the muzzle. As a result, most 8.6 Blackout loads utilize expensive specialty bullets lathe-turned from copper or a copper alloy.

Proponents of the 8.6 Blackout point out that the fast rotational velocity imparted by the 1:3 rate of twist enhances bullet expansion. They’re not wrong. It also enables the wide-expanded petals of those unique, purpose-built monometal bullets to impart a bit of energy via rotation momentum. Certainly, the cartridge has some inspiring characteristics; it’s unfortunate that the fast 1:3 rate of twist makes the 8.6 Blackout incompatible with many typical 0.338-inch projectiles.

Gun Compatibility

Because so much subsonic shooting is done with AR-15-type firearms, Hornady determined it was crucial to create a subsonic mid-bore that fit, functioned, and fired in standard AR-15-size receivers. This wasn’t a hard sell. Most cartridges loaded to subsonic speeds struggle with too much case capacity. Subsonic loads use very little propellant. When loaded into regular-size (for the caliber) cases, such as the .308 Win. or the 6.5 Creedmoor-based parent case of the 8.6 Blackout, those diminutive charges have excessive space. As a result, ignition and velocity consistency suffer.

Fortunately, the Grendel-based ARC case has just the right capacity. It provides ideal balance of case fill, efficiency, and consistency with heavy 0.338-inch-diameter bullets, making it a perfect fit for AR-15 platforms. In case you’re wondering, all it takes to convert an existing AR-15 chambered in 6.5 Grendel or 6mm ARC or .22 ARC to .338 ARC is an appropriate barrel. To convert a 5.56, add an ARC-size bolt and Grendel/ARC-compatible magazine.

And yes, you can get an AR pistol chambered in .338 ARC. Just imagine 20-plus rounds of .44 Magnum-level authority out of a short, handy, suppressed AR pistol or—better yet—an SBR. Be still my beating heart!

What about bolt actions? This was a burning question in my mind, since suppressed bolt-action firearms are even quieter than semiautomatics and because I’m gearing up to do some nighttime predator control with thermal optics. No surprise, any bolt-action rifle that handles 6mm ARC, .22 ARC, or 6.5 Grendel will comfortably handle the .338 ARC.

At the time of this writing, more than 30 rifle companies are already on board and producing .338 ARC firearms. Look up the .338 ARC on Hornady’s website, and you’ll find a long list of partnering manufacturers.

.338 ARC Performance

When I was first assigned to cover the .338 ARC, it had not yet been officially announced, and test rifles were nowhere to be had. I put in a call to Uintah Precision, and in short order a fine-looking UP-15 with a 16-inch barrel arrived at the local dealer.

It’s a heavy rifle, properly built for precise shooting. For those unfamiliar with Uintah Precision, the company makes bolt-action rifles built fundamentally like an AR-15. Actions feature three-lug bolts with 60-degree throws, housed in machined aluminum receiver sets. Sleek, free-floating handguards enclose the barrels—and they’re truly free-floating, since there are no gas blocks and gas tubes to drive the action.

Up top, the upper receiver features a 1913-spec optic rail in classic flat-top AR fashion, but of course there’s no charging handle and no spot for it. The fire controls on the lower receiver are exactly what you’d expect to find on an upper-crust AR-15. Both receivers are machined with distinctly upscale styling that’s attractive and functional. The Magpul PRS Lite buttstock features an adjustable cheekrest and robust, ergonomic styling. The rifle came with an AMEND2 composite magazine marked for 6.5 Grendel.

I lost no time mounting a bipod and scope so that I could step outside to my backyard range and wring out the new cartridge. Because I wanted to give the rifle its best shot at accuracy, I chose a Leupold Mark 5 HD 7-35X 56mm scope. That’s a lot more optic than I’d select for any practical uses the .338 ARC is ideal for, but it’s sure nice when you’re trying to shoot itty bitty groups.

Because every .338 ARC should wear a suppressor, and because the gun’s muzzle is threaded 5/8-24, I spun my Banish 338 by Silencer Central onto the muzzle. Then, with a few boxes of each flavor of .338 ARC factory-loaded ammo in hand, I was ready for the range.

Getting zeroed was a bit of a challenge. I bore-sighted the rifle, then made the mistake of starting with subsonic ammo at 100 yards. My shots impacted below the target and splattered mud all over it. Switching to supersonic ammo, I got on target, made a scope correction, and printed a tidy group with all three bullets touching, right on my point of aim. The following three-shot groups were similarly small. After four consecutive groups that resulted in a 0.92-inch 100-yard average, I switched back to subsonic loads.

The tightly clustered shots showed point of impact was 8.5 inches lower than with supersonic ammo. After dialing a correction into the scope’s turret, I fired three more groups of three shots each. The resulting average was even better than with the supersonic ammo, coming in at 0.81 inch.

With clinical accuracy testing complete, I crunched ballistics and dialed up—way up—for 350 yards. A half-size steel torso target beckoned. To my surprise, I made a first-round impact with the 307-grain SUB-X ammo. Even better, my following shots all impacted steel. Time of flight was impressive—it took roughly two seconds for the clank of lead on steel to drift back to my ears.

Throughout my shooting, one of my daughters was sitting nearby doing homework on her laptop. When I asked her how loud the shots were, she expressed surprise that I’d been shooting! The report was about like the sound of a mild nail gun, she told me, or an air compressor hose disconnecting. That is darned quiet!

Because it’s so new, I don’t have a ton of experience with the new .338 ARC yet. I don’t have the expertise of having taken a number of game animals with it. I haven’t recovered expanded bullets from carcasses. I haven’t fired it in semiautomatic rifles and compact AR pistols. But I’m excited about this new round and intend on getting a lot more experience with it over time.

Will it kill the 8.6 Blackout? Doubtful. That cartridge has a very devoted following. However, I predict the .338 ARC will surely be more widely available in local stores, both in ammo and in rifles. It fits in more different platforms. And I believe ammo and firearms will likely be much less expensive. Research indicates that—once again—Hornady’s cartridge designers got it right. Small but mighty, the .338 ARC could well be the best subsonic cartridge ever engineered.

UP-15 .338 ARC SPECS

• MANUFACTURER: Uintah Precision uintahprecision.com
• TYPE: Bolt-action repeater
• CALIBER: .338 ARC
• MAGAZINE CAPACITY: 10 rounds
• BARREL: 16 in.
• OVERALL LENGTH: 34.75 in.
• WEIGHT, EMPTY: 7.38 lbs.
• STOCK: Magpul PRS Lite buttstock, 15-in. handguard, Magpul MOE-K2+ grip
• LENGTH OF PULL: 13.75 in.
• FINISH: Black Cerakote on barrel and bolt, black Type 3 anodizing on aluminum parts
• SIGHTS: None, Picatinny rail on receiver
• TRIGGER: 3.3-lb. pull (as tested)
• SAFETY: Two position
• MSRP: $2,150

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