Suppressors 338 Arc / 338 Spectre Sound Testing (Decibel results)??

[SABuzzard]

Can anybody point me to testing results for 338 ARC or Spectre. I'm mainly interested in how subsonic loads meter. Ideally compare results between 9mm suppressors and 338 cal suppressors. I can't seem to find anything!

Also interested in hearing personal experience those that have fired subsonic 338 ARC/Spectre and subsonic 300 Blackout. How does 338 perform sound signature wise compared to the 300 BO?

Thanks!!

 

[Flexible Tangerine Sprite]

I have a 338 ARC and a 300 BO and an 8.6 BO and the one thing I can weigh in on is the sound level difference between what powders you use in subsonic loads. AA1680 was the recommended powder for the 300 BO when it first came out, mainly because with the original carbine length gas system, that double based powder would guarantee decent cycling with a port that also doubled for supersonic loads. AA1680 also appears as the recommended powder for the 8.6 BO that also has a carbine length gas system. I found AA1680 to be a loud powder for subsonic shooting with a can, hard to tame the muzzle report to get things real quiet, even with a can. On the other hand I have been running LilGun powder in the 338 ARC, the 300 BO and the 8.6 BO and have found that powder makes things super quiet ("hollywood quiet") and it also burns much cleaner too.

As far as cans go, I do not have a .338 can but I do have a Silencerco Omega 36M and also a 46Hybrid. The 46 Hybrid with the larger internal dimensions is a little louder than the 36M with .338 cartridges, but honestly I doubt you will see much difference between a 9mm can (.355) and a .338 can, except that most of the .338 cans are bigger and longer (i.e. for something like a .338 Lapua) so by their sheer size and length they do quiet things down more.

Robert

 

[JR1200W3]

I have both 338 Spectre and 300BO on bolt guns. In general the 300BO is noticably and objectively quieter. But barrel length and powder used matters. It's probably possible to make a 300BO louder than the Spectre/ ARC by using a shorter barrel and a slower powder that uses a larger charge. When loading quiet subs you want a powder that's going to burn in the barrel before it gets to the Suppressor. Example: 5.7gr of Hodgdon Longshot in a 16" barrel vs 9gr of Lil Gun in a 9" barrel. The difference is noticable. Using the same suppressor. That 300BO load in a 16" barrel with a TBAC 338 Ultra is the quietest sub I've been able to make. Very similar to a suppressed 22LR. A 12" 338Spectre is not on that scale of quiet.

I do not have a 338 ARC nor have I shot one but I'm going to go ahead and say there will be no suppression difference between the ARC and Spectre. They are all but the same, for any practical purpose besides bolt face and dies.

 

[mebgardner]

I have a 338 ARC and a 300 BO and an 8.6 BO and the one thing I can weigh in on is the sound level difference between what powders you use in subsonic loads. AA1680 was the recommended powder for the 300 BO when it first came out, mainly because with the original carbine length gas system, that double based powder would guarantee decent cycling with a port that also doubled for supersonic loads. AA1680 also appears as the recommended powder for the 8.6 BO that also has a carbine length gas system. I found AA1680 to be a loud powder for subsonic shooting with a can, hard to tame the muzzle report to get things real quiet, even with a can. On the other hand I have been running LilGun powder in the 338 ARC, the 300 BO and the 8.6 BO and have found that powder makes things super quiet ("hollywood quiet") and it also burns much cleaner too.

As far as cans go, I do not have a .338 can but I do have a Silencerco Omega 36M and also a 46Hybrid. The 46 Hybrid with the larger internal dimensions is a little louder than the 36M with .338 cartridges, but honestly I doubt you will see much difference between a 9mm can (.355) and a .338 can, except that most of the .338 cans are bigger and longer (i.e. for something like a .338 Lapua) so by their sheer size and length they do quiet things down more.

Robert

I have both 338 Spectre and 300BO on bolt guns. In general the 300BO is noticably and objectively quieter. But barrel length and powder used matters. It's probably possible to make a 300BO louder than the Spectre/ ARC by using a shorter barrel and a slower powder that uses a larger charge. When loading quiet subs you want a powder that's going to burn in the barrel before it gets to the Suppressor. Example: 5.7gr of Hodgdon Longshot in a 16" barrel vs 9gr of Lil Gun in a 9" barrel. The difference is noticable. Using the same suppressor. That 300BO load in a 16" barrel with a TBAC 338 Ultra is the quietest sub I've been able to make. Very similar to a suppressed 22LR. A 12" 338Spectre is not on that scale of quiet.

I do not have a 338 ARC nor have I shot one but I'm going to go ahead and say there will be no suppression difference between the ARC and Spectre. They are all but the same, for any practical purpose besides bolt face and dies.

This is great info, thanks for posting them.

Do you know which, if any, OEM ammo manufacturers make .300 BO using LilGun powder?

How did you solve the gas gun feeding issue with the .338 ARC? It seems like every test video I watch regarding .338 ARC, has some feeding problem usually attributed to the mag being used (but I have my doubts it's just the mag, but maybe also contributing factors). It's kept me from building one, and that issue appears to be stalling .338 ARC adoption.

 

[JR1200W3]

I don't have a gas gun in 338 Spectre or ARC

 

[mebgardner]

I don't have a gas gun in 338 Spectre or ARC

Yes, I appreciate the reply. You had stated about bolt guns.

I was hoping one, or both of you ( @Flexible Tangerine Sprite ) , might know answers to either or both questions.

 

[45-90]

I don't run a can on anything, but the 338 ARC and 338 Spectre are almost identical cartridges. I have both, the ARC has a tiny bit more powder capacity about a grain or grain and a half.
Their sound signature would be almost identical also... you'll notice a difference with different powders, as stated.
They are so close in case capacity I'm going for an improved version of the 338 ARC ...which will make no difference in subs but may add 50 fps to the anemic super velocities.
Loading for it now...all supers. Subs later.

Mags... I ordered 2 CMMG "338 ARC" mags. Some say 400 legend mags work, but these are 338 ARC specific.
For the 338 Spectre 6.8 ASC mags work.

 

[mebgardner]

I don't run a can on anything, but the 338 ARC and 338 Spectre are almost identical cartridges. I have both, the ARC has a tiny bit more powder capacity about a grain or grain and a half.
Their sound signature would be almost identical also... you'll notice a difference with different powders, as stated.
They are so close in case capacity I'm going for an improved version of the 338 ARC ...which will make no difference in subs but may add 50 fps to the anemic super velocities.
Loading for it now...all supers. Subs later.

Mags... I ordered 2 CMMG "338 ARC" mags. Some say 400 legend mags work, but these are 338 ARC specific.
For the 338 Spectre 6.8 ASC mags work.

This is the first I hear of a .338 ARC specific mag. Can you tell us your experience with using them?

 

[45-90]

This is the first I hear of a .338 ARC specific mag. Can you tell us your experience with using them?

They have not arrived ...yet.
Been shipped through, I'll let ya know...maybe tomorrow.
Got a shipment of 338 175 gr for supers, plus a host of other 338 bullets including Maker, 350, 300, 165 grs.

 

[45-90]

Well here are the 338 ARC mags. 2.3" internal capacity.
This is what it looks like maxed out with a 338 350 gr Maker...barley enough room.
The bullet guide lines up good on this huge bullet.
This is a modified 338 ARC with a 6.5 twist barrel. It will have a little more capacity for supers, but nothing extra for subs when limited to mag length.

 

[mebgardner]

@45-90 , I would also ask if you can tell the difference between this new mag, and say a 400 legend or other mag? Do you see any differences? Thanks.

 

[45-90]

@45-90 , I would also ask if you can tell the difference between this new mag, and say a 400 legend or other mag? Do you see any differences? Thanks.

I don't have a 400 Legend mag, it was recommended by some.
My regular 6.5 Grendel mags are close but these are a bit different in the bullet area.

When loading up around 6 cartridges in Grindel mags with even short pointy bullets do not push out by hand as easily as the 338 ARC mag, made for the cartridge.
But they may work for say loading 5 rds of light pointy 338 bullets...but where one may be in trouble is likely the 300 gr and especially Hornadys blunt 307 gr. bullet.

I'll know when I start shooting a variety of ammunition.

 

[45-90]

The CMMG 338 ARC mags work great in my gun.
It's now a 338 ARC improved with 6.5 twist 16" barrel.
Shooting shortened starline grendel 1.370" brass cases or fireformed 338 ARC.
To improve the speed of the high velocity rds., but not effect the subs.
175 gr at 2200 fps
200 gr Speer at 2100 fps
250 gr Hornady RN 1770 fps
300 SMK at 1100 fps, right on the edge...
350 Maker slow at 660 fps did not lock the bolt carrier back but ejected the empty.
A good day at the range, most everything went as planned.
The 350 maker is a lot of bullet as is for this 338 ARC, doesn't appear it will reach desired velocity with available powder space.
So either cut the hollow point back or run boreriders extra long COAL with cutout mags. Then 340 grs is about max that way.
Some experimentation need here or just run the 307 gr Hornaday.

 

[mebgardner]

The CMMG 338 ARC mags work great in my gun.
It's now a 338 ARC improved with 6.5 twist 16" barrel.
Shooting shortened starline grendel 1.370" brass cases or fireformed 338 ARC.
To improve the speed of the high velocity rds., but not effect the subs.
175 gr at 2200 fps
200 gr Speer at 2100 fps
250 gr Hornady RN 1770 fps
300 SMK at 1100 fps, right on the edge...
350 Maker slow at 660 fps did not lock the bolt carrier back but ejected the empty.
A good day at the range, most everything went as planned.
The 350 maker is a lot of bullet as is for this 338 ARC, doesn't appear it will reach desired velocity with available powder space.
So either cut the hollow point back or run boreriders extra long COAL with cutout mags. Then 340 grs is about max that way.
Some experimentation need here or just run the 307 gr Hornaday.

Really appreciate you taking time to post this info up. Thank You!

Is there anything else "improved" besides the 6.5 twist? Who made this barrel for you?

Those 350 Makers (cut to 340) are promising with a SD of less than 3. Yeah, 2 shots recorded, but promising.

Which primers is all that's missing from the shot build cards, that I can see.

 

[45-90]

The Hornady 338 ARC vs My version 338 ARC improved....just to let people know it has a bit more capacity for supers and higher velocities....but little effect on subs, as the long bullets take up most of the powder capacity, which is a good thing giving nice velocity spreads.
So it's a compromise, can't make the case too long like full grendel length and fit a 350 gr bullet in the mag.
But I wanted to see if this small increase in powder volume would give me the extra velocity over the Hornady factory specs for the 175 gr bullet. Like the 6 br VS the 6 Dasher. So far I'm running the 175 gr at 2200 fps ave VS factory 2075 fps from a 16" factory test barrel.

I used Rem 7 1/2 primers for all loads.

The 350 Makers are factory untouched bullets that weigh 347 grs.

I don't hunt anymore these days but I do test bullets on paper, to see what's possible and share the information with others who are interested.
It's up to them to decide if they want to incorporate any of it into their loading or shooting disciplines.
I considered improving the velocity of 660 fps which only has a little way to go with this powder...but they are quiet.
To increase velocities in limited space of case capacities and mag lengths, ya gotta use cutout mags, cutoff .060" or so of the hollow point only about 6 grs, or single load boreriders all machined in lathe collets and stops.
All that can be done...along with try a couple of other powders.

I chambered this 6.5 twist 338 barrel from a take off SS barrel it's 16" long.
Took 6 months to get the reamer, and there was a $40 price increase.
Carbine gas .122" port.
Did not adjust gas from the 660 350 gr sub to the 2200 fps 175 gr.
But the 350 sub 660 fps charge would eject the case but not lock the bolt.
Everything else ran 100% 300 gr SMK subs to 175 gr supers.
These 338 ARC CMMG mags are no compromise they feed blunt 250 gr RN 100% also.

The load data for subs should work for standard 338 ARC, the supers take out a couple grains to make sure, cause here is where the extra capacity shows up, as tiny cartridges build pressures fast, so pay attention to seating depth.