6.8 SPC for suppression?


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LRS_Ranger
February 9, 2010, 11:36 AM
I was wondering if the 6.8 would be a good option for suppression. Is anyone running a can on their 6.8? Is there a better option for an AR type weapon without going to a full blown .308 or a pistol round? I would like to look into subsonic as well; sub-5.56 ammo just doesn't have much knockdown power tho. Any pointers?

This has probably already been hashed and rehashed here, so if you can link me to a thread with all the magical internet advice I need that would be great. :D

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essayons21
February 9, 2010, 01:14 PM
Check out the 300 Whisper

gunhistory501
February 9, 2010, 01:46 PM
A friend has a Barrett 6.8 with the Barrett suppressor. Without the suppressor you can feel the shock-wave from the rifle when standing next to him. With the suppressor the rifle sounds like an unsuppressed .22 pistol and the sound of the bullet breaking the sound barrier comes from some distance downrange. The suppressor also seems to tame down the felt recoil. After firing this rifle I think a suppressed 6.8 is an excellent idea.

Arkady
February 9, 2010, 01:55 PM
6.8 suppresses fairly well--almost as well as 5.56.

Most of the 6.8 cans out there are bored-out 5.56 cans. AAC, Surefire, and Ops all make 6.8 suppressors, but finding hard data on db reduction levels can be difficult.

LRS_Ranger
February 9, 2010, 02:02 PM
Are there any good subsonic 6.8 loads out there?

LiquidTension
February 9, 2010, 02:10 PM
Check 68forums.com for load recipes.

Shadow Man
February 9, 2010, 02:11 PM
Are there any good subsonic 6.8 loads out there?

6.8x43mm is still in its infancy as a cartridge, and commercial loads for it are few and far between as it is. A more specialized subsonic loading would be difficult to find if it is even manufactured. Barrett Rifles has a 6.8 carbine, 6.8 magazines, and a few other goodies, so you may have some luck looking there.

Just out of sheer curiosity, why do you want a subsonic load?

LRS_Ranger
February 9, 2010, 02:38 PM
The only suppressor experience I have is with 5.56, and I never got a chance to try a subsonic load with it. It sounded a lot like a 22LR, most of the sound coming from the bullet and the action making a clack-clack sound. If you get the bullet subsonic it should be pretty quiet. The only problem with subsonic 5.56 is that by slowing it down you just took the one thing that 5.56 has going for it, and that's its velocity. With a bit heavier caliber you should be able to use a lot heavier bullet and thereby make up for the loss in velocity to some extent. I was just hoping someone had already experimented and came up with a solution.

Shadow Man
February 9, 2010, 02:44 PM
Well, you're never going to eliminate the noise of the action unless you are firing a suppressed bolt action. The subsonic loads eliminate the sonic boom, or crack, down range but do this by sacrificing powder loads, therby decreasing range and velocity and increasing bullet drop. So, I guess the question is: how quiet do you want to go, and how far do you want to be able to shoot?

Of course, by your previous post, I know you understand all of that, I was merely reiterating it for my own benefit.

Float Pilot
February 9, 2010, 05:23 PM
I have loaded 150 grain round nose bullets into the 6.8SPC (270 Kurtz) and have been able to load them just below the sound barrier around 1125 fps over my chrony. They must be single loaded, but they were pretty accurate at 100 yards, considering. They were pretty quite even without a can.
I also loaded the same bullet up to 1,975 fps from a 16 inch barrel. (the same that a 30-30 16 inch trapper carbine will do) But it would not feed reliably....

Dr. Tad Hussein Winslow
February 10, 2010, 01:21 PM
Well, you're never going to eliminate the noise of the action unless you are firing a suppressed bolt action. The subsonic loads eliminate the sonic boom, or crack, down range but do this by sacrificing powder loads, therby decreasing range and velocity and increasing bullet drop. So, I guess the question is: how quiet do you want to go, and how far do you want to be able to shoot?

Of course, by your previous post, I know you understand all of that, I was merely reiterating it for my own benefit.

Bingo.

If you want QUIET in a semi-auto, the 6.8 spc is fine and dandy.

If you want REALLY quiet, in a semi-auto (at the expense of a bit of oomph), then you want .300 whisper (aka .300 fireball), or better yet, .338 spectre (to minimize loss of 'oomph').

If you want REALLY REALLY quiet, then you want .300 whisper or .338 spectre in a TURNBOLT, not semi-auto.

Shadow Man
February 10, 2010, 05:14 PM
6.8SPC has been compared to the 6.5Grendel since its conception, and one of the usual talking points during the debate that inevitably arises is that the Grendel has a much higher BC, allowing it to buck wind much more efficiently than the SPC. By shooting a subsonic load, you are reducing the amount of velocity pushing the round, so the SPC's ability to resist wind drift will be even less than it was with a full-power loading. I only mention this because it will seriously effect the practical accuracy of the platform.

Also, I checked the Barrett Rifle site, and they do not manufacture subsonic 6.8x43mm ammunition. A quick search through the larger manufacturers turned up zero results as well, so I'm inclined to think that to have a subsonic 6.8x43mm round, you will have to load it yourself.

LiquidTension
February 10, 2010, 05:28 PM
Subsonic loads in 5.56 will not cycle the action so the action noise is a moot point. I don't think subsonic 6.8s would cycle the action either, but I do not have one so I can't say for sure. Just for reference, a subsonic 5.56 suppressed sounds basically the same as a suppressed .22lr and has the same velocity (obviously due to speed of sound) but the bullet is twice as heavy. 1,050 fps is a good threshold to aim for in subsonic loads, as the speed of sound drops with temperature. I fired one off in the back yard that was subsonic in the summer, then forgot to take that into account when it was really cold one night.

Thank goodness suppressors mask the location of the shot :uhoh:

Zak Smith
February 11, 2010, 01:20 AM
Heck, my original article from 2006 showed a 6.8 SPC with a can on!

http://demigodllc.com/photo/6.8SPC-sgn/smaller/B100_0263_img.jpg (http://demigodllc.com/photo/6.8SPC-sgn/?small=B100_0263_img.jpg)
............... Larger version of above photo. (http://demigodllc.com/photo/6.8SPC-sgn/?small=B100_0263_img.jpg)


http://demigodllc.com/photo/6.8SPC-sgn/icon/B100_0601_img.jpg
article | 6.8 mm SPC Cartridge History and Development. Hornady's 6.8 SPC ammunition. The Stag Carbine. http://demigodllc.com/icon/extwh3.png (http://demigodllc.com/articles/6.8-mm-spc-cartridge-history-development-hornady-stag-arms-carbine)

The posters above are pretty much on.

I think the problem with heavy subsonic loads in 6.8 will be insufficient barrel twist.

Other than that, run your favorite ammo/loads through your can on your 6.8 and have fun. Note that the standard 5/8-24 threads on the 6.8 allow most .30 caliber suppressors to screw directly on and the suppression level is very good.

Shadow Man
February 11, 2010, 09:32 AM
Wait, you wrote that article, Zak!? I read it with great interest when it first came out, and couldn't wait to try an AR chambered in 6.8x43! Sadly, I never did, and that was four years ago, but that's pretty cool. A very informative write-up sir, thank you!

MatthewVanitas
February 11, 2010, 10:17 AM
Most of the 6.8 cans out there are bored-out 5.56 cans. AAC, Surefire, and Ops all make 6.8 suppressors, but finding hard data on db reduction levels can be difficult.

Since a 6.8 is .27", would it work decently well with a .30 suppressor?

Some THR member posted a pic of a can he had which was "based on designs intended for the M14", which was rather fat but quite stubby, and I thought it'd be kinda neat to see on a 6.8mm Mini-14. Plus them maybe I could get a .30 Whisper T/C barrel and use it on that too. What with $200 tax, I'd like to keep my cans as versatile as possible.

I know it's pretty common to shoot through suppressors intended for larger calibres, and I'd assume that shooting 6.8 through a .30 can would suppress better than shooting .223 through a .30 can. Am I thinking right here?

Dr. Tad Hussein Winslow
February 11, 2010, 10:43 AM
Subsonic loads in 5.56 will not cycle the action so the action noise is a moot point.

Are you sure about that?

They may not *cycle* the action (i.e. eject the spent casing and load a new round), but it seems to me that they'd have enough gas to unlock the action and push the bolt back a *little bit*, both of which make noise, as well as the bolt coming back forward and re-locking.

Shadow Man
February 11, 2010, 10:46 AM
They may not *cycle* the action (i.e. eject the spent casing and load a new round), but it seems to me that they'd have enough gas to unlock the action and push the bolt back a *little bit*, both of which make noise, as well as the bolt coming back forward and re-locking.

To be honest, I've never fired subsonic 5.56x45 before, however I'm pretty sure that adjustable gas plugs would allow the user to compensate for firing a lower powered subsonic round.

Zak Smith
February 11, 2010, 01:01 PM
Since a 6.8 is .27", would it work decently well with a .30 suppressor?
Yes, it will work very well, though the suppressor will be "full size".

To be honest, I've never fired subsonic 5.56x45 before, however I'm pretty sure that adjustable gas plugs would allow the user to compensate for firing a lower powered subsonic round.
I don't think you can make this work with normal-length gas systems in .223. .300 Whisper can run the action but it has a pistol-length gas system.

-z

Shadow Man
February 11, 2010, 01:10 PM
I don't think you can make this work with normal-length gas systems in .223. .300 Whisper can run the action but it has a pistol-length gas system.

Okay, that makes sense, thank you for the clarification. So would you even be able to run a subsonic round out of an AR platform, like the OP wants to?

Zak Smith
February 11, 2010, 02:00 PM
Well, he asked it 6.8 SPC was a good option for suppression, and then he was interested in looking into subsonic as well. 6.8 SPC would be as good a candidate for full-power suppressed loads as anything in the AR-15 platform, actually a bit better than 5.56 (it's "less overbore"). For subsonic, making subsonic loads run an AR-15 action is always a problematic venture, and I am skeptical it could be made to work with a stock barrel and gas system setup. You can always shoot subsonic loads that don't run the action.

If you're building a dedicated upper for subsonic use, .300 Whisper/Fireball is a better choice. From a 10.5" .300 FB barrel, I can shoot 125's at 2100+ fps, 150's at 1850 fps, or 240's at 1100 fps (sub). All of these run the action.

-z

WoofersInc
February 11, 2010, 02:44 PM
Subsonic loads in 5.56 will not cycle the action so the action noise is a moot point.


While at Shot Show I was talking with the rep in the Extreme Shock ammo booth. He was stating that they have a 100 grain subsonic 5.56 round that will run the action on carbine length guns. He said they are still playing to get it to run a full length rifle gun.

They are now showing it on their webpage.

http://www.extremeshockusa.com/cgistore/store.cgi?page=/new/product_info.html&setup=1&cart_id=

USAMP1980
September 29, 2011, 10:44 AM
If I may add:
6.8 and 6.5 Grendel work great out of a .308 can, no noteable loss in performance.
I too doubt you can get 6.8 to cycle, at least not reliably or easily.
If the weapon does not successfully perform all 8 cycles of function, I would not say it cycles.
I would not buy the Extreme Shock 100 grains. I tried it in: mid length, carbine, and a SBR. I even tried cutting down a buffer spring. No matter what I tried, the result were the same. It consisently ejected the brass, but did not pick up the next round. It is also expensive. About one round per 20 box failed to chamber. Every time I had to drop the lower and pound the bolt in. After forced extraction, it left the projectile in the barrel... which come out easily with a cleaning rod. I would not trust this ammo on an operational level.
However, it was very quiet (for a .223/.224)... and the CQB accuracy was fine. On my Matech BUIS, I moved the selector from 300 to 200 meters and was good to go at 25 meters.

68wj
September 29, 2011, 10:49 AM
Well, since the thread managed to be reawakened, how about this?
http://www.youtube.com/watch?v=-5goJthhYGM

brian923
September 29, 2011, 01:04 PM
Im so gelouse, i wish i lived in a free state! If your like me, and like to buy something that can be used for more than on application, a 30 cal full size can would work with multiple guns instead of just one. I hope Com'inois will eventually let us get supressors, bit i highly doubt it. We cant even concel carry! I hate this state.

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