Thread: 338 ARC - An Early Guess At Reloading Data

I can supply Hornady 338 Arc dies, they are in the country

Here is some Hornady load data

https://static.hornady.media/site/ho...ta/338-ARC.pdf

I have some 128gr Stone Hammer projectiles showing up in the coming week for my 8.6 x 47 Lapua with its 11-12" barrel

Will be interesting to see the velocity availible from them compared to around the 2550 fps with the 160 TTSX

Hard to believe I've had it 6 years now, man time flies

Kiwi Greg those Stone Hammers sound real interesting, any spare ? I'd be interested in trying some in the ARC now that Ive gone and ordered a reamer.

I'll be using the 161gr OEP which is about 1mm shorter than the 160gr TTSX, goal is to try and get them up to around 2450fps from a 21 inch tube.

Will have die sets on the shelf too in the next few days.

Hodgdon have put up some data on their site too.

Originally Posted by Pommy

Will have die sets on the shelf too in the next few days.

Hodgdon have put up some data on their site too.

Thanks for the heads up Pommy, I hadnt seen any reference yet for the 160gr projecitles so good to see Hornady putting that out.

Originally Posted by Pommy

I've got dies. Forming brass from 6.5 Grendel is quite doable...

Attachment 276049

Those ones were not neck turned and came out too thick though. Having access to an annealing machine makes it much easier too.

So assumable from 7.62x39 would be easier still??? Less of a jump up in bore size. Thinking the data from this cartridge wouldn't be huge way off the x39 with heavy weights...very little out there for x39 once get over 150 is why I ask,ponder,muse on this.

The two downsides to using 7.62x39 brass that I found were 1 that 7.62x39 has more taper in the body which means the cases have more fireforming to do than just sharpening up the shoulder. And 2 the brass tends to be large primer which definitely won't last as long as small primer when loaded up to bolt gun pressures. Still, I may grab myself a box of Lapua x39 brass to experiment with using large pistol primers, since there's no sign of any more Lapua Grendel brass coming in.

Supersonic performance on the 338 might be kind of comparable to x39. But it's a bigger frontal area and more mass with subsonics on the 338... 30cal 255gr SubX vs 33cal 307gr SubX... There's also the 9x39 which you could compare to. But only on paper because there's bugger all projectiles to choose from if you build one of those.

Honestly, if you are going with a 338 arc, the capacity is so small, I am not sure it’s even necessary to waste time and money with light supersonic projectiles. The 338br , 8.6 bo and 338 federal would be probably better for that dual/ purpose role .

Originally Posted by Friwi

Honestly, if you are going with a 338 arc, the capacity is so small, I am not sure it’s even necessary to waste time and money with light supersonic projectiles. The 338br , 8.6 bo and 338 federal would be probably better for that dual/ purpose role .

Yes the capacity is small and speeds will be moderate, but low recoil, low noise and killing ability under 150m should be pretty decent. I hunt small blocks where 90% of game are shot at distances of less than 150m. I can confirm that both the 175gr HP and 307gr Subs feed well from the factory Howa mini magazine.

Originally Posted by Friwi

Honestly, if you are going with a 338 arc, the capacity is so small, I am not sure it’s even necessary to waste time and money with light supersonic projectiles. The 338br , 8.6 bo and 338 federal would be probably better for that dual/ purpose role .

If the ARC can get the light projectiles up to enough speed to make it effective out to a couple hundred metres, that's not a waste of time. Of course the bigger cases will drive those bullets faster, easier. But you can't do an 8.6 or a 338 fed on something like a Howa Mini. And Hornady's point is that those cases have too much capacity to do subs consistently.

Pulled 1 of the 307gr Subsonic out last nite and water capacity of the 338 ARC case is a massive 30.6gr, prob 31.0gr when fired formed.

2300fps is probably a more realistic goal with 2205 than 2400fps according to Qkld with the 161gr projectiles I'll be using. 1:7 twist should still give expansion out to 400m......

Hi, just for info, I m getting 2400 fps with Barnes 160 gr and around 30 grains of vita n110 in my 8.6 blackout with an 18” tube.
At 31 grains I am over pressure.

Originally Posted by Friwi

Hi, just for info, I m getting 2400 fps with Barnes 160 gr and around 30 grains of vita n110 in my 8.6 blackout with an 18” tube.
At 31 grains I am over pressure.

thats pretty interesting, I would have thought N110 was a bit on the fast side but I havent followed the 8.6BLK tbh, Id imagine 2205 and 07 would also work ?

My 128 Stone Hammers turned up this morning



338 Grendel, 338 BRX, 8.6 Blk, 8.6 x 47 with 128 Stone Hammer & 160 TTSX, 338 Federal, 128 STH & 160 TTSX

Interesting to see the cases side by side as they step up in volume

My old 338 BRX 20" upper launched the 160 TTSX the same speed as its replacement the 11.75" 8.6 x 47 at 2550 ish fps

Will be interesting to see how much more velocity over the 160 TTSX I can get out of the 128 STH

Originally Posted by Billo

thats pretty interesting, I would have thought N110 was a bit on the fast side but I havent followed the 8.6BLK tbh, Id imagine 2205 and 07 would also work ?

So when I was laddertesting the 8.6 with n110, between 29 and 32 grains, I was getting about 60fps of increasing speed per grain.
And also I tried Reloader7, and I was getting only 2150fps maximum. So not as efficient. I have not tried other powders.

Originally Posted by Friwi

So when I was laddertesting the 8.6 with n110, between 29 and 32 grains, I was getting about 60fps of increasing speed per grain.
And also I tried Reloader7, and I was getting only 2150fps maximum. So not as efficient. I have not tried other powders.

Thanks, seems a whole new world using pistol powders with short modern rifle cartridges thou I must confess I was playing with AR2205 and a 44 WSSM wildcat back in 2011