All the rage right now are AR-15-style carbines that shoot quietly. Why? Because they are more fun for the shooter and less disturbing to everyone else. Hence, we are witnessing a proliferation of suppressors used with subsonic rounds in low-recoiling calibers such as 9mm and 300 Blackout. But there is only one real problem with traditional-caliber subsonic rounds: They are not great for hunting because their downrange energy is dismal. Can you kill wild hogs with a subsonic 300 Blackout round? Yes, but here are the facts:
A subsonic, 220-grain 300 BLK round delivers around 540 ft.-lbs. of energy at the muzzle and just 495 ft.-lbs. at 100 yards. (Not too long ago, most serious hunters considered the .30-30 Winchester a marginal round much past 100 yards, and it has 1,350 ft.-lbs. of energy at that range.) Anecdotally, I once shot a 267-pound wild boar at 50 yards with a subsonic 300 Blackout round, and it failed to even fully penetrate the hide of the near-side shoulder. Can you kill them, yes. Is it ideal? No.
So, since subsonic speed is exclusively a product of a projectile’s speed and must be kept under the 1100 fps threshold, a subsonic projectile’s energy can only be increased by increasing the projectile’s weight. This is the main reason why Hornady engineered the 338 ARC. But first, a little history of the ARC, or Advanced Rifle Cartridge.
From left to right 170-grain Monoflex, 175-grain HP, 215-grain FTX and 307-grain Sub-X.
Back in 2020 Hornady released its 6mm ARC after years of experimentation in trying to meet the demands of the U.S. Special Operations Command (SOCOM). It wanted a lightweight rifle cartridge that would fit in M4-style carbines with little alteration and would be capable of delivering a 50 percent hit ratio on man-size engagements at 2,000 yards from an 18-inch barrel.
Hornady necked down a 6.5mm Grendel case to .243 diameter, filled it with specialized, blended powders and topped it with one of its own super-high BC ELD bullets. It’s a great little cartridge that performs bigger than it looks. Next, Hornady introduced the 22 ARC for long-range varminters and target shooters. Then in 2025, Hornady released its 338 ARC that utilizes many of the same design principles. But instead of being a high-velocity round meant for long-range work, a much heavier 307-grain subsonic bullet would provide more energy than a 300 Blackout yet, unlike its rival the 8.6 Blackout, it could still be fired from a lightweight AR-15 platform by only changing out the barrel, bolt and magazine.
Hornady’s proprietary round—spearheaded with a 307-grain SUB-X bullet—is touted to launch at 1050 fps for 752 ft.-lbs. of energy at the muzzle and 658 ft.-lbs. at 100 yards. The bullet capitalizes on many years of Hornady’s research by using an optimized polymer tip and skives that initiate and control expansion, even at low velocities. For a subsonic caliber that is very quiet when combined with a suppressor, these numbers (about twice that of a 9mm Luger round) aren’t too shabby.
Hornady also offers several supersonic loads, including one I tested, the Hornady Black label that sends a 175-grain hollowpoint match bullet at 2075 fps for 1,673 ft.-lbs. of energy at the muzzle and 1,370 ft.-lbs. of energy at 100 yards. Again, this is impressive when you consider that these numbers are derived from a 16-inch barrel. The entire cartridge appears to be more bullet than case with an overall cartridge length of just 2.26 inches. And that’s exactly why Hornady designed it. The Grand Island, Neb., company knew that to produce a cartridge that would fit into an AR-15 platform with little necessary conversions, yet still be accurate and reliable, it must be built on a small case (head diameter .441 inch; overall case length 1.3 inches; 30-degree shoulder) that would pack the powder together without large air pockets forming within the case that could cause velocities to be inconsistent from shot to shot. The small case would increase accuracy potential as well as cycling reliability. As such, the little case only holds around 9.5 grains of powder! Talk about efficiency!
As of the time of this writing, more than 30 firearm companies are chambering guns for the 338 ARC, with more to come. This bodes very well for the stubby new cartridge, because all too often such brand-new, not-well-received cartridges only garner the attention of two or three gun companies that are willing to take a risk. This equals fewer options for shooters and higher costs, which frequently spells a death sentence.
I chose CMMG’s very interesting Dissent rifle, an AR-hybrid carbine that combines the action of an AR-15 with ergonomics and controls closer to a traditional rifle. For hunting it’s great because it’s not quite as angular and clunky as an AR-15 in the woods. It comes with a 10-round mag. The rifle I chose wore a 16-inch barrel, and I outfitted it with a Rugged Alaskan Ti 36 suppressor for much of the duration of my testing. Here’s what I found:
Living every day in wild hog country, I do have a real desire for a subsonic round that packs more of a wallop than a 300 Blackout, because I have seen firsthand that in some cases on large hogs at marginal shot angles, a subsonic 300 Blackout won’t do. So I welcomed the 338 ARC’s extra foot-pounds of energy while remaining about as quiet as possible with modern suppressor technology … which is to say that while my 338 ARC setup’s noise profile falls well under the threshold for safe shooting without hearing protection, don’t be fooled into thinking it’s like a subsonic .22 rifle where all you hear is the action and the thud of the bullet. It’s quiet, but it’s not silent.
And although I tested for accuracy on a windy day and with a low-power scope, accuracy wasn’t tack-driving, but acceptable for such a short-range hunting gun, which is exactly what this is. In whole though, I like the new caliber and the rig; it’s a great lightweight AR-sized plinker that delivers killing energy downrange. Inside a home it would be deadly, while for shots at 100 yards and in on deer and hogs, it’s just fine.
Basically, if I had to choose between the 300 Blackout, 8.6 Blackout or this 338 ARC as a do-all, subsonic AR-15 option, I’d choose the 338 ARC, especially considering the two subsonic options from Hornady cost about the same at $30 per box of 20. My only question is: What’s next? The 400 ARC? Only time will tell.
Hornady 338 ARC
- hornady.com
- Caliber: .338
- Action Length: AR-15, micro bolt-action
- Bullet weights and types available in factory loads: 175-gr. HP Match (tested); 307-gr. Sub-X (tested); 170-gr. MonoFlex; 215-gr. FTX; 285-gr. FMJ
- Ballistic coefficient (G1): .385 (307-gr. Sub-X); .375 (175-gr. HP Match)
- Muzzle Velocity: 1050 fps (307-gr. Sub-X); 2075 fps (175-gr. HP Match)
- Muzzle Energy: 752 ft.-lbs. (307-gr. Sub-X); 1,673 ft.-lbs. (175-gr. HP Match)
- Uses: hogs, deer, medium-size game
- MSRP per box: $34.99
