338 ARC

[Ledzep]

Looking through the different .338 cal cartridge performance classes, 338 ARC seems to be a 338 Marlin Express that fits in an AR-15. It should be a hammer both with supers and subs.

Could get interesting with purpose-built lower expansion threshold monoliths.

The other thing I like is you have high mag capacity with heavy-hitting loads. It will be interesting to see if mags need stronger springs like 300 Whisper does for the significantly-heavier cartridge stack once you start talking about 25-30rd mags.

@45-90 do you have any 25rd ASC Grendel or 30rd Geissele 6mm ARC/Grendel mags?

@Ledzep what capacity magazines did you guys test with the AR-15s? I know in the podcast that there was discussion about how well they fed and cycled, which surprised some of the people who shot them in ARs.

Let me touch base with some folks about that. I have been loosely involved with the bullet (307 sub-x) but haven't done much with weapons systems. I know that MDT 6mm ARC AICS pattern magazines work well with it in a bolt gun, but I'll double check on the AR-15 front. I'd imagine mostly 10-17 rounders, and I think I heard the E-landers' guide rib pokes inside too far but we're talking with them and several other companies at this point to make compatibility as good as possible.

 

[JR1200W3]

The 350 gr Maker may not even be able to be used....have to see if max velocities top out before expansion maybe as low as 600 to 800 fps. Soon we will know....

You better not post anything that didn't kill an animal

 

[45-90]

I was looking at Hornady’s data for the .338 Marlin Express, and they’re showing a 200gr FTX at 2400fps from a 24” barrel out of a lever gun.

Hornady is saying 2075fps from a 16” barrel for the 175gr in 338 ARC.

When I drop the barrel length for that 200gr .338 Marlin down to 16”, it gives me 2232fps.

This is the closest of the legacy .338s I could find to 338 ARC performance, comparing Lever gun pressure to AR-15.

The 338 ARCs closest competitor is the 300 blackout....the 175 gr sectional density is equal to about 143 gr in 30 cal.
So at this point the 300 Blackout is a better supersonic round than 338 ARC.
The 300 Blk about 4 grs less powder capacity 26 gr to 30 gr but 10,000 psi advantage.
As a result my 300 blkout 16" barrel runs 175 gr Nosler RDF at 1922 fps out of a factory barrel. The 338 ARC runs 2075 out of a factory test barrel... but in reality is probably 100 fps less in your auto loader.
Which puts them at the same enery level, but the 30 cal 300 blackout 175 gr has a much higher BC and sectional density than the 338 175 gr Hornady. So it will over take the 338 in energy and penetration with such a light supersonic bullets in the 338 ARC.
Just the facts....So why bother with the 338 ARC?
It's its subsonic potential with 300 gr bullets, for superior accuracy. Cause small capacity and good case fill should be clean powder burns at higher pressures and more consistent velocities than other subs.
For hunters the 300 gr expanding billets offers more energy and larger diameter for the possibility of larger wound channel capability, than the 300 blackout.

 

[45-90]

You better not post anything that didn't kill an animal

I ain't gonna kill any game animal with it, (maybe an unlucky rabbit) ....that will be up to you.
But I'll test it for velocity to even see if it falls within the narrow expansion specifications of the maker.
My personal concern is excellent accuracy with the 300 gr match bullets, and possibly others, when tested. Mostly targets and a few short range rabbits tests.

 

[clcustom1911]

I'm waiting to see what all the hornady haters will say because its always fun to see people spaz out. When I saw the podcast title at first I thought it was going to be some type of short action magnum for AR10's. When I saw it was just a subsonic primary AR15 round with more kinetic energy I was a little disappointed but I look forward to seeing how it does against Pigs.

It'll be the same people who 10-12 years ago clowned on the 6.5 Creedmoor and said it would die after a year or two.

 

[Gtscotty]

That makes things a little more interesting for us poors, I could see myself getting a daily deal upper to play with at some point, especially with some cheap AAC fodder to run.

Palmetto State Armory on Instagram: "338 ARC WHEN?? We’re proud to announce that we’ll be partnering with @hornadymfg to bring you 338 ARC options👀From new developments in the JAKL and Sabre lines to ammo from AAC, this project is going to be big! S

3,670 likes, 291 comments - palmettostatearmoryofficial on October 28, 2024: "338 ARC WHEN?? We’re proud to announce that we’ll be partnering with @hornadymfg to bring you 338 ARC options👀From new developments in the JAKL and Sabre lines to ammo from AAC, this project is going to be big! Stay...

www.instagram.com

 

[rlsmith1]

TELL THE MARKETING PEOPLE WE WANT 6ARC FIRST!!!!!

I'll probably get a 338 ARC if PSA is making ammo for it (after I get 1k of their 6 arc)

 

[JR1200W3]

TELL THE MARKETING PEOPLE WE WANT 6ARC FIRST!!!!!

I'll probably get a 338 ARC if PSA is making ammo for it (after I get 1k of their 6 arc)

..teach a man to fish....

XL750

The Dillon XL750 is a high-speed progressive reloading machine designed to load common rifle and handgun cartridges from .17 Hornet though the common belted magnum cartridges in rifle and .32 ACP through .500 S&W in handgun. The XL750 comes with a lifetime warranty against manufacturing...

www.dillonprecision.com

 

[rlsmith1]

..teach a man to fish....

XL750

The Dillon XL750 is a high-speed progressive reloading machine designed to load common rifle and handgun cartridges from .17 Hornet though the common belted magnum cartridges in rifle and .32 ACP through .500 S&W in handgun. The XL750 comes with a lifetime warranty against manufacturing...

www.dillonprecision.com

Looked into that and then looked at what I would spend on an autodrive and autotricklers and it just got to be more of a hassle than I wanted to deal with. But I hear you, reloading at scale is a superpower!

 

[JR1200W3]

Looked into that and then looked at what I would spend on an autodrive and autotricklers and it just got to be more of a hassle than I wanted to deal with. But I hear you, reloading at scale is a superpower!

I just wanted you to know there was a legal way to be free from factory ammo availability

 

[45-90]

So I've been waiting on 338 ARC just to try it. Still waiting on reamer, brass, dies etc.

So after looking into the 338 Spectre and finding they are almost identical in performance.

I looked on line, and behold everything is available for it, barrels with bolt included, dies, brass, etc.
So I ordered the components needed, and in a few days it's together.
Dies and 600 rds of brass will be here on 2 days. Brass is much cheaper than Hornaday, and available now.
So one can have the 338 ARC in the form of the 338 Spectre today... if interested.

Checked the thickness of the brass, to see where to run the pressure, it will be 55,000 psi in this case.

 

[45-90]

338 Spectre is rated for 46K PSI
Will 338 ARC have similar pressure rating as 6 ARC (62K bolt and 55K AR) ?

I just finished a 338 Spectre today everything was available on line, barrel with bolt, dies, brass, I ordered and the rifle is already together.
Still waiting on the 338 ARC reamer.
I milled a 224 Valkyrie in half at the cartridge head to compare with the Starline 10 mm Mag pistol brass, they are the same...the 6.8 SPC cartridges in the AR are rated at 55,000 psi the AR 338 ARC is 52,000 psi.
You can get SR cases or Pistol primed cases. I got some of each, They are much cheaper than Hornady 338 ARC cases.
So I already ran the load data to 55,000 psi on my 338 Spectre...so we'll see.

 

[JR1200W3]

I don't understand the mystery. Load 8-9gr of Lil Gun for 300gr subs. That's it. This has already been stated in this thread.

Unless you're trying to figure out supersonic speeds. And that's why you're worried about chamber pressure. But that's a losing battle in this case. It's not the cartridge for supers. The 8.6BO is going to beat it all day. And the 8.6 isn't impressive either. It'll take a normal person about 20 mins of analysis to land on 375 Raptor for supersonic performance...in a subsonic capable cartridge.

 

[45-90]

I don't understand the mystery. Load 8-9gr of Lil Gun for 300gr subs. That's it. This has already been stated in this thread.

Unless you're trying to figure out supersonic speeds. And that's why you're worried about chamber pressure. But that's a losing battle in this case. It's not the cartridge for supers. The 8.6BO is going to beat it all day. And the 8.6 isn't impressive either. It'll take a normal person about 20 mins of analysis to land on 375 Raptor for supersonic performance...in a subsonic capable cartridge.

I'm try to "figure out" supersonic, as well as what's possible with different powders in subs.
Same as I do for all the mostly subsonic cartridges, some times considered dual purpose, but they are not impressive in high velocity for the most part, compared to high velocity hunting cartridges.
Depends on the platform, AR 15, AR 10, or bolt gun.
I have the 300 blk, 8.6 blk, 338 Spectre, 450 Bushmaster 16 twist for 500 gr subs I consider pretty good for a sub gun just resize the 458 bullets.
I run 200 gr bullets to 2600 fps in 8.6 BLk in 6.5 twist & 2800 fps for 160 Barnes, 225 gr 2407 fps, 250 gr Speer GS 2200 fps. 300 gr Berger 1970 fps, 350 gr Maker 1675 fps.
Plus run them subsonic.
But my 510 Whisper takes the prize for pure energy, subs can have 2600 ft/lbs of muzzle energy, with bullets at over 1000 grains in subsonic mode. 750gr and 900 gr Maker for hunting subs, or 4700 ft/ lbs to over 5000 ft/lbs for lighter supers.
It all depends on what one wants and what platform you intend to use, and if one tends to explore all the possibilities of a tiny sub cartridge or any cartridge for that matter...that's what I do, cause I want to know...others may only be interested in subs.

 

[LRRPF52]

I just finished a 338 Spectre today everything was available on line, barrel with bolt, dies, brass, I ordered and the rifle is already together.
Still waiting on the 338 ARC reamer.
I milled a 224 Valkyrie in half at the cartridge head to compare with the Starline 10 mm Mag pistol brass, they are the same...the 6.8 SPC cartridges in the AR are rated at 55,000 psi the AR 338 ARC is 52,000 psi.
You can get SR cases or Pistol primed cases. I got some of each, They are much cheaper than Hornady 338 ARC cases.
So I already ran the load data to 55,000 psi on my 338 Spectre...so we'll see.

I have a New Frontier Armory 6.8 Receiver set and Magpul Six8 PMAGs that might be interesting to try in that.

I don’t have any interest in doing a 6.8 or .224 Valkyrie, but a .338 Spectre might make sense. Mags might need to be modified.

The mag well is quite a bit larger on the Six8 receiver sets, as are the mags. They are wider and longer (COL).

 

[KCode]

What do you guys think about the Nosler Accubond 180gr 338 for some good 300 yard and in AR15 hitting power in this new cartridge?

 

[st1650]

What do you guys think about the Nosler Accubond 180gr 338 for some good 300 yard and in AR15 hitting power in this new cartridge?

I highly highly doubt it'll go fast enough for expansion at 300 yards
This isn't the right cartridge for hunting at 300 yards.

 

[LRRPF52]

What do you guys think about the Nosler Accubond 180gr 338 for some good 300 yard and in AR15 hitting power in this new cartridge?

Accubonds typically require 1800-2000fps impact velocities to expand.

At 2075fps from a 16”, I doubt it will have any expansion threshold in it. Expensive ice-pick at that point.

 

[M4guru]

I have a New Frontier Armory 6.8 Receiver set and Magpul Six8 PMAGs that might be interesting to try in that.

I don’t have any interest in doing a 6.8 or .224 Valkyrie, but a .338 Spectre might make sense. Mags might need to be modified.

The mag well is quite a bit larger on the Six8 receiver sets, as are the mags. They are wider and longer (COL).

You will need to trim the neck guide ribs down, but they will work otherwise.

 

[45-90]

Maker has expanding bullets already for the 338 Spectre 6.5 twist 165 gr that are supposed to work in the 2100 fps to 900 fps range, plus a 215, 225, 275, 300 gr.
but they are not for the 3 twist or the 8 twist barrels...they are 6.5 twist specific.
All bullets would have to be tested for velocity versus expansion.
I do not plan to hunt with it.
For me these subs are fun plinkers.
I just put together an AR 15 on 338 Spectre, brass, dies, & cartridge gauge arrive tomorrow.
It's a balistic twin of the 338 ARC but components, dies, brass, and barrels and uppers are available now, and a lot cheaper than Hornaday 338 ARC brass, for those interested.

 

[KCode]

Accubonds typically require 1800-2000fps impact velocities to expand.

At 2075fps from a 16”, I doubt it will have any expansion threshold in it. Expensive ice-pick at that point.

Do we know muzzle velocities yet? I haven't seen. 2075fps out of a 16" seem very low for 180gr.

 

[LRRPF52]

Do we know muzzle velocities yet? I haven't seen. 2075fps out of a 16" seem very low for 180gr.

Hornady lists a 175gr supersonic load in the Black line that does 2075fps from a 16” barrel.

I’m only interested in the shorter barrels since there is no reason to go longer than needed for subs, and this is really a subsonic design intent cartridge.

 

[45-90]

I ordered all the stuff for the 338 Spectre and most everything arrived in 7 days.
The rifle is done, about 7 days to ship the barrel.
Received 600 pcs of brass, dies, Wilson cartridge gauge, and 6.8 PRI magazines.
The 338 ARC is very similar to the 338 Spectre...almost identical. A side by side, but not exactly....as I do not know where the neck shoulder junction is for the 338 ARC, but a mockup of the ARC compared to a factry 338 Spectre.
I have both pistol and SM primer cases.
Brass is cheap 100 for $46 Spectre cases, 10mm Mag pistol cases by 500 or 1000 quantities, anneal and run through die really cheap no trimming necessary
Half to one third the price of the unavailable Hornady brass....you can afford to loose a few with an autoloader.
Also have some Maker bullets coming.
My 338 ARC reamer is still on order...but everything is available for 338 Spectre ...now. For what it's worth.
I'm gonna run the Spectre for awhile, see if I like it. Since the performance is basically the same...

 

[JR1200W3]

The pistol primer pocketed brass won't tolerate much pressure. I wouldn't advise anyone to buy any. If the 338 ARC is made with rifle brass, that alone is enough reason to wait for the ARC and go with that.

 

[KCode]

So this will basically ONLY be a subsonic round?

 

[45-90]

The pistol primer pocketed brass won't tolerate much pressure. I wouldn't advise anyone to buy any. If the 338 ARC is made with rifle brass, that alone is enough reason to wait for the ARC and go with that.

You haven't been paying attention, the 338 Spectre Has SR primers, and run at 55,000 psi same as the 6.8 SPC.
If you make them out of 10 mag they will obviously have pistol primes...I have both!
The pistol brass is 46,000 psi but starline has increased the case web to the same as the SPC rifle brass...I milled one into to confirm.
Do not spread misinformation...
Make an informed choice.
The Spectre SR brass is sold by the 100ps bag and 1/2 price of the Hornady brass.
Plus on most sub loads ya won't use the high psi on any of the brass, depending on the powder.
Just the facts, plus I'm gonna run the pistol brass to 55000 psi to see how it stands up with the pistol primers. I run them to 65,000 psi in 454 Casull running heavy bullets in 45Colt brass.....45 Colt brass has a thicker webb than 44 mag, on Win brass when milled and measured.

Here are the SR primed 338 Spectre brass for those interested. All the components are available now

 

[JR1200W3]

You haven't been paying attention, the 338 Spectre Has SR primers, and run at 55,000 psi same as the 6.8 SPC.
If you make them out of 10 mag they will obviously have pistol primes...I have both!
The pistol brass is 46,000 psi but starline has increased the case web to the same as the SPC rifle brass...I milled one into to confirm.
Do not spread misinformation...
Make an informed choice.
The Spectre SR brass is sold by the 100ps bag and 1/2 price of the Hornady brass.
Plus on most sub loads ya won't use the high psi on any of the brass, depending on the powder.
Just the facts, plus I'm gonna run the pistol brass to 55000 psi to see how it stands up with the pistol primers. I run them to 65,000 psi in 454 Casull running heavy bullets in 45Colt brass.....45 Colt brass has a thicker webb than 44 mag, on Win brass when milled and measured.

Here are the SR primed 338 Spectre brass for those interested. All the components are available now

I also have both brass from SBR Munitions. I bought the pistol brass first and then the SR brass because I was losing primer pockets loading subs. I was just trying to be nice to you once and let you know not to waste your time with the pistol brass. I guess fuck that.

You're posting long diatribes about buying barrels and dies like you're the first person pioneering the Spectre trying to maintain your tinker extraordinare/ maven status. I've been shooting it for over a year. Go ahead and post your results with the large primer brass like it's news but I already told you. I bet you will lose the primer pockets on the large primer brass experimenting with subs. And the people on the 338 Spectre FB group already know it as well. It's only going to be news to you.

 

[45-90]

I also have both brass from SBR Munitions. I bought the pistol brass first and then the SR brass because I was losing primer pockets loading subs. I was just trying to be nice to you once and let you know not to waste your time with the pistol brass. I guess fuck that.

You're posting long diatribes about buying barrels and dies like you're the first person pioneering the Spectre trying to maintain your tinker extraordinare/ maven status. I've been shooting it for over a year. Go ahead and post your results with the large primer brass like it's news but I already told you. I bet you will lose the primer pockets on the large primer brass experimenting with subs. And the people on the 338 Spectre FB group already know it as well. It's only going to be news to you.

So why not say, use the SR brass instead of the of LP brass, in the 338 Spectre, in your experience.
You said, LP brass won't hold the pressure, for that reason alone, you would wait for the 338 ARC.
Not saying anything about SR brass being available for the 338 Spectre.
Misleading folks who might consider the 338 Spectre, telling them to wait for the 338 ARC because of SR primer.
I do not care which one people choose, just what's available for them to make the right choice for them.
I have s 338 ARC reamer ordered, but the 338 Spectre is almost identical. So I'll shoot it and see what I think, with both SR and LP primers.

 

[JR1200W3]

Screenshots from the 338 Spectre/ RB/ARC FB group. A fella shot a large whitetail buck at 200yds with a 300gr Maker from a Spectre and dug the bullet out.

I swear, the way that bullet expanded looks familiar....

 

[Ledzep]

So this will basically ONLY be a subsonic round?

I wouldn't say that. Won't be the biggest baddest .338 supersonic cartridge ever but I'd imagine there will be expanding supersonic options for it in the future...

 

[JR1200W3]

So why not say, use the SR brass instead of the of LP brass, in the 338 Spectre, in your experience.
You said, LP brass won't hold the pressure, for that reason along, you would wait for the 338 ARC.
Not saying anything about SR brass being available for the 338 Spectre.
Misleading folks who might consider the 338 Spectre, telling them to wait for the 338 ARC because of SR primer.
I do not care which one people choose, just what's available for them to make the right choice for them.
I have s 338 ARC reamer ordered, but the 338 Spectre is almost identical. So I'll shoot it and see what I think, with both SR and LP primers.

Because I'm not convinced of SBRs SR brass either. I think their brass may be soft but I haven't gotten through multiple firings on the 300 pieces I've bought to really see. And I think it remains to be seen how long SBR supplies it. They may have bought a huge batch from a brass manufacturer and it could be a one time availability. So If your option is to form it from also extinct 10mm Mag brass vs buying brass that you know is made from rifle brass a person should probably choose between the near identical cartridges based on brass quality and long term supply.

 

[45-90]

Because I'm not convinced of SBRs SR brass either. I think their brass may be soft but I haven't gotten through multiple firings on the 300 pieces I've bought to really see. And I think it remains to be seen how long SBR supplies it. They may have bought a huge batch from a brass manufacturer and it could be a one time availability. So If your option is to form it from also extinct 10mm Mag brass vs buying brass that you know is made from rifle brass a person should probably choose between the near identical cartridges based on brass quality and long term supply.

So, SBR SR brass may be soft, but you're not really sure.
Let me know when you find out.
I will never run out of SR brass for the 338 Spectre, as I have a bunch of new 224 Valkyrie brass to make 338 Spectre cases out of, if I want... plus many others with that head diameter.
I have 1200 6mm ARC cases none have a 6mm ARC headstamp, 250 have no head stamp, just Starline grendel basic. Because it took forever for Hornady to get 6 mm ARC cases to the reloaders.
I never shoot a factory load in any rifle.
Example grindel basic annealed will become 6mm ARC, and 250 6mm ARC no headstamp.
Never out of brass ... serious brass making, milling to length, neck turning 900 pcs, 510 whisper cases.
The 338 Spectre or 338 ARC are easy, there are always cases available, but they may have to be modified. Head turning and extractor grooves recut, even 308 to 6mm ARC is possible but alot of work.
I make quite alot of brass for obsolute calibers. If ya depend on others, many times ya have a long wait.

 

[ohnomrbillk]

Hmmmmm......what about a 175 gr projectile out of a 338 Lapua Improved...maybe 4000 fps?

Old school 338 cal 160 nosler ballistic tip.

338 Lapua Ackley 40 degree

30 inch barrel

Load for 300 gr SMK in formed brass was 100 gr retumbo, IIRC

Same load on the 160 gr went 3600 fps ish. Room for more, but those little bullets didn’t love the 9.3” twist barrel, so never went more.

Tested on white tail deer with chronic wasting disease.

There was ZERO suffering.

 

[45-90]

So purchased the 338 Spectre barrel & cheap brass waiting on 338 ARC reamer.
Went out and shot it, after waiting for the weather to clear, it was cold.
Tried both SR & LP primed cases.
Pushed the Speer 200 gr bullet to 1900 fps in the LP primed cases...need to back off to 1800 fps for this bullet, and pistol cases.
It was very accurate with subs 200 gr and 300 gr SMK with pistol primed cases.
Ran the 160 gr 338 Barnes to 2141 fps with the SR cases, which is too warm, 2080 fps might work out well for this combo, it's accurate.
Also ran the 350 gr Maker at 880 fps in SR cases as the pressure moves up fast in tiny volume cases with heavy bullets. This was an accurate combination.
350 gr Maker turned the bullet point 9° angle and cut .060" off the hollow point to fit mag lenght in AR15...So the orginial 350 gr Maker was actually weighed 346 gr and modified it was 340 gr. fit snugly into the AR 15. With no cutout magazine
Bulk of the reloading was done on a Dillon progressive with thrown charges. H110 and LilGun were the powders used.
Fired brass SR cases 29 4 gr. H20.
Fired brass LP cases 29.5 gr. H20.
This 338 Spectre barrel has a 6.5 twist Hornady 338 ARC an 8 twist barrel.
This 338 Spectre shot everything well I tried 160 gr Barnes to 350 gr Maker, I was impressed for the first time out.
The 338 ARC may have a grain or two more powder, but these are basically the same.

 

[putput30]

So purchased the 338 Spectre barrel & cheap brass waiting on 338 ARC reamer.
Went out and shot it, after waiting for the weather to clear, it was cold.
Tried both SR & LP primed cases.
Pushed the Speer 200 gr bullet to 1900 fps in the LP primed cases...need to back off to 1800 fps for this bullet, and pistol cases.
It was very accurate with subs 200 gr and 300 gr SMK with pistol primed cases.
Ran the 160 gr 338 Barnes to 2141 fps with the SR cases, which is too warm, 2080 fps might work out well for this combo, it's accurate.
Also ran the 350 gr Maker at 880 fps in SR cases as the pressure moves up fast in tiny volume cases with heavy bullets. This was an accurate combination.
350 gr Maker turned the bullet point 9° angle and cut .060" off the hollow point to fit mag lenght in AR15...So the orginial 350 gr Maker was actually weighed 346 gr and modified it was 340 gr. fit snugly into the AR 15. With no cutout magazine
Bulk of the reloading was done on a Dillon progressive with thrown charges. H110 and LilGun were the powders used.
Fired brass SR cases 29 4 gr. H20.
Fired brass LP cases 29.5 gr. H20.
This 338 Spectre barrel has a 6.5 twist Hornady 338 ARC an 8 twist barrel.
This 338 Spectre shot everything well I tried 160 gr Barnes to 350 gr Maker, I was impressed for the first time out.
The 338 ARC may have a grain or two more powder, but these are basically the same.

Looks like a good performer with that twist rate. Is that with a 16inch barrel or did you go shorter?

 

[45-90]

Looks like a good performer with that twist rate. Is that with a 16inch barrel or did you go shorter?

It's a 16" barrel.

 

[david walter]

In the 338 ARC just 10mm pistol brass necked down? Or do I misunderstand?

I just finished a 338 Spectre today everything was available on line, barrel with bolt, dies, brass, I ordered and the rifle is already together.
Still waiting on the 338 ARC reamer.
I milled a 224 Valkyrie in half at the cartridge head to compare with the Starline 10 mm Mag pistol brass, they are the same...the 6.8 SPC cartridges in the AR are rated at 55,000 psi the AR 338 ARC is 52,000 psi.
You can get SR cases or Pistol primed cases. I got some of each, They are much cheaper than Hornady 338 ARC cases.
So I already ran the load data to 55,000 psi on my 338 Spectre...so we'll see.

 

[hseII]

In the 338 ARC just 10mm pistol brass necked down? Or do I misunderstand?

Based on a 10mm Magnum &/or 6.8 spc.
You can use either.

 

[Ledzep]

Based on a 10mm Magnum &/or 6.8 spc.
You can use either.

No, the 338 ARC is .445" Grendel/7.63*39 parent. The spectre is .421".

 

[bly]

This 338 Spectre barrel has a 6.5 twist Hornady 338 ARC an 8 twist barrel.

I,m wondering if 8 twist is sufficient if you want to shoot say 300 gr SMK subsonic?

Here is 300 gr SMK at 300 meters in minus 5 degrees Celsius from a 7 twist barrel:

It’s not making a round hole, and if you look at several bullet holes in the same group, they’re entering whit different angles through the paper

At this point they don’t group well either..

 

[hseII]

No, the 338 ARC is .445" Grendel/7.63*39 parent. The spectre is .421".

I misunderstood his question- I thought he was asking about the Spectre.

 

[Cascade Hemi]

Spectre is based on 10mm Auto or SPC, not 10mm Mag.

 

[hseII]

Spectre is based on 10mm Auto or SPC, not 10mm Mag.

A 10mm Auto is too short to be the parent case of the .338 Spectre, which has a case length of 1.250.

338 Spectre | The Ballistic Assistant

www.theballisticassistant.com

 

[45-90]

Based on a 10mm Magnum &/or 6.8 spc.
You can use either.

No the 338 ARC is .441-442" the 338 Spectre is .421 to .422" head area diameter. Grindel vs 224 Valkyrie, 6.8 SPC, 10MM Mag pistol, or 30 Remington, cut to length. With a short case their water capacities are very close. With in a grain or two, with only .019" to .020" different in head diameter. How deep the bullet is seated will make a big difference in either case.

 

[45-90]

View attachment 8548093
A 10mm Auto is too short to be the parent case of the .338 Spectre, which has a case length of 1.250.

338 Spectre | The Ballistic Assistant

www.theballisticassistant.com

No its Starline 10 mm magnum, which are perfect... no trimming just anneal for best results and run through your 338 Spectre FL die $68 per set. Use on all sub loads up to 300 gr SMK then switch to SR cases the highest velocity for supers. They are so cheap ya don't care of ya lose a few.

 

[45-90]

I,m wondering if 8 twist is sufficient if you want to shoot say 300 gr SMK subsonic?

Here is 300 gr SMK at 300 meters in minus 5 degrees Celsius from a 7 twist barrel:
View attachment 8547951
It’s not making a round hole, and if you look at several bullet holes in the same group, they’re entering whit different angles through the paper
View attachment 8547950
At this point they don’t group well either..

The 8 twist is on the low end for subs with long 300 gr match bullets...a 7 twist should work according to Berger stability calculator.
But that doesn’t matter if you're have trouble.
So try a shorter bullet like the 250 SMK to see if things improve.
Hornady’s 307 gr sub is likely much shorter and will stablize in a 8 twist. But none are available, yet.

 

[st1650]

The 8 twist is on the low end for subs with long 300 gr match bullets...a 7 twist should work according to Berger stability calculator.
But that doesn’t matter if you're have trouble.
So try a shorter bullet like the 250 SMK to see if things improve.
Hornady’s 307 gr sub is likely much shorter and will stablize in a 8 twist. But none are available, yet.

Has Hornady said publicly if they were going to release that bullet as standalone component in 2025 ?

 

[roosterpig]

SURELY they aren’t dumb enough to withhold it.

 

[45-90]

Has Hornady said publicly if they were going to release that bullet as standalone component in 2025 ?

Hornady will release components after they get factory ammo up and running. They always do ...just way late and huge shortages, just like all the rest of their cartridge introductions.. Their projected prices for cases is pretty high for such a tiny case.

 

[45-90]

The SR Spectre brass and 10 mm Mag brass have basically the same case volume#1 & #2.
They all have the same solid head thickness 338 Spectre, 10 MM Mag, 224 Valkyrie, and the 6.5 Grendel.
I used the same collet to mill all the fired cases including the 6.5 Grendel, so the diameters of the fired cases are close enough for one collet to fit both.
So logically the brass head hardness, and alloy, plus firearm design will be the only factors in ability to take pressure, since they are all the same thickmess in the solid head.