TESTED: NEW 338 ARC (Odin Works Rifle + Hornady Ammo)

The all new 338 Cartridge from Hornady offers more – more versatility, more efficiency, and more downrange energy compared to alternatives like 300 BLK. Let’s look at this cartridge, and put it to the test! How will it stack up against what it promises? Check it out in this story!

Disclaimer

Ultimate Reloader LLC / Making with Metal Disclaimer: (by reading this article and/or watching video content you accept these terms). The content on this website (including videos, articles, ammunition reloading data, technical articles, gunsmithing and other information) is for demonstration purposes only. Do not attempt any of the processes or procedures shown or described on this website. All gunsmithing procedures should be carried out by a qualified and licensed gunsmith at their own risk. Do not attempt to repair or modify any firearms based on information on this website. Ultimate Reloader, LLC and Making With Metal can not be held liable for property or personal damage due to viewers/readers of this website performing activities, procedures, techniques, or practices described in whole or part on this website. By accepting these terms, you agree that you alone are solely responsible for your own safety and property as it pertains to activities, procedures, techniques, or practices described in whole or part on this website.

About 338 ARC

Whenever a new cartridge is released to the general public, I like to get my hands on it, test it, and bring those insights and results to you. Hornady just released 338 ARC – this is a 338 Caliber Advanced Rifle Cartridge platform. It’s similar to 6 ARC in that it shares that 6.5 Grendel case rim diameter, but it actually predates the development of the 6 ARC. It was put on the shelf, and then brought back out and released recently!

The cartridge is meant to take some of the shortcomings from 300 BLK. Some of these challenges in cartridges like 300 BLK have been high SD numbers, velocity variation, gas settings between subsonic and subsonic configurations, the powder burn, and the down range energy.

338 ARC is here to address these areas, and more. For example, a 338 ARC is able to utilize a 307 grain projectile, about 100 grains more than something like 300 BLK. Yes – this cartridge was designed with the AR15 in mind, so it’s got a 2.260” cartridge OAL max. This way it can fit in a standard AR15 magazine (The magazine is going to be the same as a 6.5 Grendel or 6 ARC). Also, even though this is a new cartridge, it doesn’t take much to step into as there’s a good degree of interoperability with components for the AR-15 platform that are already on the market.

Hornady Factory 338 ARC Ammo (Subsonic & Supersonic)

So what I have here is a limited quantity of the 2 SKUs of ammo Hornady is offering for the platform. 175 grain BLACK Ammo, and 307 grain Sub-X (Get it at Midsouth Shooters Supply!) – Supersonic and subsonic respectively. Find out more about this ammo here:

From Hornady:

“The BIG little cartridge that packs a punch!
Purposefully designed for hard-hitting subsonic performance, the 338 ARC delivers 1.5 times more energy than the 300 Blackout Subsonic. Engineered for consistent pressure, the 338 ARC provides consistent and reliable cycling with both super and subsonic loads. Featuring the 307 gr. SUB-X bullet in the SUBSONIC line and the 175 gr. HP in BLACK, the 338 ARC represents the ultimate 338 cartridge that fits in an AR 15 or micro-bolt action.”

Odin Works 338 10.5” Rifle

For testing, we’ll be running an Odin Works rifle that I put together. Odin just announced their offering for 338 ARC Barrels.

They’re offered in 10.5” and 16.1” in 1:8 Twist. That’s great; Hornady recommends that 1:8 twist. Odin will also be offering complete uppers – however, I’m not sure about complete rifles. I will keep you posted on that!

This rifle is equipped with the Odin Close Quarters Pistol Brace, an Aero Lower, with a Hogue over-molded grip. We’ve got the 10.5” complete upper, and the Odin Enduro Suppressor. This is a modular suppressor, and I’ve taken a couple baffles out of that suppressor so we could get the overall length down a bit. I really like the way this rifle came together. It’s handy, compact, it’s suppressed, and it’s going to be a great way to test this new cartridge. I topped it with a Leupold Mark 5HD 2-10; this scope should be perfect (Check out our dedicated video & article on this scope for more).

Initial Testing & First Impressions

To run through the paces, I had to zero the rifle, get some chrono data, take it to distance, and shoot enough to determine if 338 ARC would run reliably with both ammos – subsonic & supersonic without having to do any tuning. How did it go?

I’m impressed! I sighted-in at 50 yards. Because I only had 2 boxes of each SKU of ammo, I had to really be conservative with my ammo. Fortunately, the sight-in went smooth!

After sight-in, I then just calculated my dope accordingly for the extended range shooting. We set up at the 200 yard rock chuck (steel target from D-M targets) to evaluate the relative performance between the subsonic and supersonic ammo. 200 yards is actually a pretty good reach for such a close quarters optimized platform. What I noticed after shooting at 200 yards is that the recoil was a lot lighter on the 307 grain subsonics. However, both SKUs performed great!

Speaking of close quarters, we also took this setup to the industrial yard. There, I engaged some closer targets, and had a ton of fun!

Overall, this rifle package is a great setup. This retractable Close Quarters Pistol Brace is awesome. The Enduro Suppressor offered great performance. It was really quiet with this subsonic ammo.

Considerations

Feeding

I noticed the 307 grain Sub-X bullet has a very blunt point, and from a factory 6.5 Grendel magazine the round was hitting below the feed ramp. I had to take a pair of pliers and open up the front of the magazine. That enabled the round to sit back, angled up a bit. That enabled the AR to reliably and consistently feed the subconic rounds.

This is an interesting optimization problem. This is a nose heavy bullet, especially compared to what the AR platform was originally designed for. But, a little bit of adjustment allowed both the subsonic and supersonic rounds to feed reliably! Another note, pointed subsonic bullets probably would not have been an issue at all. We’ve used Berry’s 220gr bullets for example, in 300 BLK subsonic loads (see that story here).

Adjustable Gas Block

We did have an adjustable gas block – but we did not have to adjust at all! That was great confirmation that the promise of 338 ARC was living up to what the claims were.

Velocity

The velocity looked really good overall. However, our chronograph only picked up 2 shots of the subsonic ammo. So, we have limited data. Between those 2 shots we had a 1,045 fps average, SD of 2.6, and an ES of 5.1. I hadn’t realized we only picked up 2 shots, otherwise we would have kept testing! For the supersonic, we had 5 shots averaging 1,926.6fps, an SD of 7.8, and an ES of 22.6. Overall – that’s what we were looking for!

Conclusion

So at the end of the day, what’s my first impression with 338 ARC? I love it! It lives up to the claim – it is in fact an efficient cartridge with a shorter barrel, good velocity. It’s easy to shoot when you reach out a bit (like 200 yards), and it works well with existing components. As I mentioned before, the Leupold Mark 5HD performed really well on this setup. So what’s next?

As a follow up we may look at a bolt action build. If you’re interested in that, let me know!