Anyone going with the 338 ARC?

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Feb 20, 2025
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I have a couple of different .223 Uppers that I rarely shoot, so I'm thinking of rebarreling one of them to .338 ARC. I'm mainly interested in shooting subsonic, so I'm not sure if I'll go with a 10.5" barrel or a 16" barrel. It might just come down to which length barrel I find in stock first, since I don't have a strong preference either way.

I have a few boxes of factory ammo and a couple Grendel magazines, already. I still need a barrel, BCG, and some reloading dies. I don't know how long I'll have to wait for the Hornady 338 SUB-X to be released in component form, so until then, I might try and burn through my old stash of 200gr Ballistic Tips.

Is anyone else planning to try out the .338 ARC?
 
Sounds like you have the perfect use case. Myself, no interest. I already have rifles set up for sub hunting. It isn’t big enough caliber for me to deer hunt, so I went with a 358 socom instead. Same concept, just more case capacity and bigger bullet.
 
MidwayUSA got some business from me the past couple of weeks. I put together a 338 ARC with a 14.5" Faxon barrel and Faxon bolt. I also bought a set of Hornady 338 ARC dies, brass, and a few of their factory-seconds bullets appropriate for this cartridge.

The extractor tension on the Faxon bolt was a bit much. A few rounds fed and chambered properly, but the bolt didn't fully close, because the extractor didn't snap over the case head. I saw some significant marks on some the case rims, so I removed the o-ring under the extractor, and the issue went away.

I also noticed the fired brass casing came out fairly battered and dented. Even the cases caught in the brass catcher net showed significant signs of abuse. This was more evident in the supersonic loads, versus the subsonic loads, so I think the pistol length gas system and the stiff ejector spring were both to blame. I didn't have the means to tinker with the ejector spring at the range, but I shortened it, once I got home. I hope this helps.

Here are the first few cases I fired, with dinged up case mouths on the 175gr Black ammo.
Xuvwcom.jpg


Here are the case mouths from factory Sub-X ammo (top) and 175gr Black ammo (bottom). The cases from the subsonic ammo are in better shape, but stilled dented.
xT6mbjr.jpg


Here are the case heads from factory 175gr Black ammo:
7PaazPJ.jpg



The factory 175gr Black ammo showed very consistent velocities, 2042 fps average, ES of 12, and SD of 4 (for a 6-round string). I couldn't match it with my 175gr handloads with Lil' Gun powder and WSR primers (5-shot strings).
18gr Lil'Gun, 1816 fps ave, ES = 20
18.5gr Lil' Gun, 1859 fps ave, ES = 22
19.0gr Lil' Gun, 1896 fps ave, ES = 22
19.5gr Lil' Gun, 1977 fps ave, ES = 38


The factory Sub-X Ammo wasn't as consistent, velocity-wise, and 2 of the 5 rounds didn't fully cycle without the suppressor. The empty round was ejected, but the bolt didn't come back far enough to pick up the next one. All five rounds cycled properly with the suppressor, though.
5-rounds without the suppressor:
1010 fps ave, ES = 51

5-rounds with the suppressor:
1028 fps ave, ES 38


I also loaded some 250gr BTHP bullets with Lil' Gun powder. I forgot to reset the chronograph for the last two strings, so I don't have data for the 12gr and 12.5gr loads. The 12gr load was the most accurate, with 5-shots touching, so I will load some more at this charge weight and run them again.
11.0gr Lil' Gun, 1091 fps ave, ES = 28
11.5gr Lil' Gun, 1134 fps ave, ES = 43


Here are the groups with the 175gr HP loads, both factory ammo and handloads:
wFHjxz9.jpg


Here are the groups with 250gr handloads and factory Sub-X ammo:
dwmd6pj.jpg



Aside from the extractor issues and subsonic/unsuppressed loads, previously mentioned, I didn't have any other stoppages. The .400 Legend Duramag seems to work great with the 338 ARC.

I have some 300gr BTHP bullets headed my way, and I haven't loaded the 250gr BTSPs I picked up with my first order (I hope they shoot well, because they were dirt cheap). I also have some 200gr Ballistic Tips I want to try.
 
Seems like a fun round, but my 300 BLK is much cheaper to feed compared to 338 projectiles.

I can’t say I won’t ever try it, but probably won’t be anytime soon.
 
I have a AR build to do and plan on a howa build too.
I'm also impatiently waiting on the 307's to be sold as components.
 
Here are the first few cases I fired, with dinged up case mouths on the 175gr Black ammo.
Xuvwcom.jpg


Here are the case mouths from factory Sub-X ammo (top) and 175gr Black ammo (bottom). The cases from the subsonic ammo are in better shape, but stilled dented.
xT6mbjr.jpg
Thats classic 'shortened casing clipping the brass deflector' deformation.
I had the exact same issues with my .300blk until I glued a little rubber wedge to the face of the shell deflector.

All brass ejected from an AR suffers the same impact, but with full length cases it hits in the center where the case is stronger so it doesn't deform.
 
Thats classic 'shortened casing clipping the brass deflector' deformation.
I had the exact same issues with my .300blk until I glued a little rubber wedge to the face of the shell deflector.

All brass ejected from an AR suffers the same impact, but with full length cases it hits in the center where the case is stronger so it doesn't deform.
Thanks for the info!

Some of the case mouths were dented so badly, I wasn't sure they were going to be reusable. The dent actually rolled/curled inside the case mouth, so I used the shank of a screw driver get the dent mostly straightened out before running them through the sizer die. They all look useable, though!



I'm also impatiently waiting on the 307's to be sold as components.
Yep, me too!
 
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