338arc made by Valkyrie Rifles
- Thread starter AM_Lillycombe
- Start date
Am just in the process of building a barrel in this to go on my 6.5Grendel Sako 75
No idea why but I need one!
No idea why but I need one!
Sounds like its made for the job!
tackb
Well-Known Member
thats awesome !
impressive kills at that range with that velocity , i wonder what scope he is using because 5-10 yards either way on the range would be a miss !
AM_Lillycombe
Well-Known Member
I did look at the 458 socom but there was a reason why I went with 338arc. Can’t remember now.
I think it was ballistics (338arc carries energy for a good distance) plus it’s backed by a major ammo manufacturer. Is a socom an AR10 round where as the 338arc is AR15 (cant remember):
You need 450gr .458 at subsonic speeds to reach 1000ftlbs of energy.
The guys at Q have done some exstensive 8.6 creedmoor testing in Africa both sub and super. They have shot hundreds of animals, it works well with the correct projectile.
The guys at Q have done some exstensive 8.6 creedmoor testing in Africa both sub and super. They have shot hundreds of animals, it works well with the correct projectile.
AM_Lillycombe
Well-Known Member
8.6 blackout was a firm no from my fire arms officer. I’m also not comfortable with the 1in 3 twist the Q recommend, I couldn’t find any data if anyone tried 1in6 or similar. So on both counts it ruled it out for me.
AM_Lillycombe
Well-Known Member
So I finally managed to get to a range with the 338ARC to do some load development.
While the trajectory may be shaped like a banana, I would say that it seems to be a very accurate/consistent round.
With 270 gr ELDX travelling at 1045 FPS my last two 5 short groups were ragged holes at 100 m. I’m sure that is nothing to some of you sharp shooters on here. But for me that’s the best two groups I’ve ever done!
Much more recoil than I expected, but not a manageable. Seemed quite loud, but then again it was a covered range. The aero precision ar15 is quite noisy to cock/chamber.
Using a standard Duramag 6.5 Grendel magazine it fed perfectly other than maybe twice when the bolt didn’t catch the back of the cartridge to push it forward so needed a second attempt to chamber a round.
Once I get some more rounds made up, I will do some photos and video.
While the trajectory may be shaped like a banana, I would say that it seems to be a very accurate/consistent round.
With 270 gr ELDX travelling at 1045 FPS my last two 5 short groups were ragged holes at 100 m. I’m sure that is nothing to some of you sharp shooters on here. But for me that’s the best two groups I’ve ever done!
Much more recoil than I expected, but not a manageable. Seemed quite loud, but then again it was a covered range. The aero precision ar15 is quite noisy to cock/chamber.
Using a standard Duramag 6.5 Grendel magazine it fed perfectly other than maybe twice when the bolt didn’t catch the back of the cartridge to push it forward so needed a second attempt to chamber a round.
Once I get some more rounds made up, I will do some photos and video.
Cold Forged
Member
Out of interest, did your FEO give any specific reason for refusal?
AM_Lillycombe
Well-Known Member
Because it has no official approval in any country and because it can be loaded to far exceed uk hunting requirements (more in the line of dangerous game rather then pest control).
I’m not displeased with the refusal because my 338arc is far exceeding accuracy expectations. And i have another gun for supersonic shooting so i don't need this gun to do both.
Cold Forged
Member
A "civilised" and accurate 8.6 Blackout - sounds perfect to me.
AM_Lillycombe
Well-Known Member
Gosh don’t say that anywhere else on the internet!!! The anti Hornady brigade will be hunting you down with pitchforks!
22xm1
Well-Known Member
At risk of offending sensitivities, I think the .338 arc is nearer to the .300 BO rather than the 8.6, because, hear me out, the .300 and the .338 both go in an AR15 platform, whereas the 8.6 is an AR10 platform.
But, then again, no hands-on time on any of those 3 calibers, but that's what I can see from my perspective.
But, then again, no hands-on time on any of those 3 calibers, but that's what I can see from my perspective.
AM_Lillycombe
Well-Known Member
I agree! but only if talking supersonic. The 8.6BO got standardised by Saami yesterday BTW!!!!
300 blackout can achieve 1400ft lbs.
It's possible load a 338arc to go over 1700ft lbs without exceeding powder capacity or recommended max pressure.
The 8.6blackout has factory ammo available that can push over 2500ft lbs! So home load probably even more.
So yes you are 100% right... but then again at high velocity you wouldn't want their recommended 1 in 3 twist rate because the spin will far exceed the limits of the projectile.
With subsonic loads, (Keep in mind that subs are the whole point of this for me) extra powder capacity is neutralised or even a drawback due to the chance of inconsistent powder burn.
338 spectre, 338 ARC and 8.6 Blackout, All are the same knock down power and frontal area. They all fire a 300gr+ projectile to a muzzle energy of around ~750ft lbs. The 300BO is only 450 to 500 ft lbs subsonic at the muzzle and decelerates faster than the heavier projectiles. So what you say is not the case when it comes to subsonic.
An 8.6 BO with a 1 in 6.5 twist rate and a digital scope that has 2x profiles (one for subs and one for supers) would be a very versatile weapon.
For subsonic only 338 arc has the edge because it has Hornady behind it and it has the smaller case capacity.
I do wish I built mine into a classic hunting style rifle rather than the ar15 because the ar is noisy.
AM_Lillycombe
Well-Known Member
I've just read this in an article:
"As of January 2026, SAAMI has formally standardized the 8.6 Blackout cartridge. While the adoption itself is significant, one detail in the published SAAMI print stands out and will likely surprise many shooters familiar with the cartridge’s origins. The recommended twist rate is 1:6, not the 1:3 twist that originally made the 8.6 Blackout famous."
"As of January 2026, SAAMI has formally standardized the 8.6 Blackout cartridge. While the adoption itself is significant, one detail in the published SAAMI print stands out and will likely surprise many shooters familiar with the cartridge’s origins. The recommended twist rate is 1:6, not the 1:3 twist that originally made the 8.6 Blackout famous."
Cold Forged
Member
Good call. Might actually save cast lead bullets from disintegrating in mid air!
Penyard
Well-Known Member
Having had a custom .308 that was designed to shoot heavy subsonic bullets for 15 years, I recently sold it having concluded a long time ago that heavy subsonic bullets are not as useful as I once thought they might be and a very serious ricochet risk.
I would be particularly concerned using a subsonic rig like this in environments where a ricochet could be a big problem. It’s a different world in the US with big open spaces but in the UK I’m not sure the trade off of reduced noise is worth the price of the much increased ricochet risk if horses, livestock or houses are in the vicinity.
Looks a really smart build and don’t wish to rain on the parade but do be careful as slow big heavies have a serious tendency to bounce.
I would be particularly concerned using a subsonic rig like this in environments where a ricochet could be a big problem. It’s a different world in the US with big open spaces but in the UK I’m not sure the trade off of reduced noise is worth the price of the much increased ricochet risk if horses, livestock or houses are in the vicinity.
Looks a really smart build and don’t wish to rain on the parade but do be careful as slow big heavies have a serious tendency to bounce.
