Loudness of a suppressed 8.5 300 BLK AR

[Crawfish1]

I wanted to see if someone has a 8.5" Blackout SBR and also a 16" Carbine length barrel 300 BLK they have shot suppressed.

I have a 8.5" barrel 300BLk and also a 16" 300 BLK and the 8.5" is loud enough shooting subs it is almost uncomfortable while the 16" is pretty quiet. I am shooting same hand loads thru both.

I have read reports that 8.5" 300 BLK was as quiet as 9mm? I am having strong doubts I can get my 8.5" to shoot near that quiet.

Does anyone shoot a 8.5" 300 BLK AR that is as quiet as a carbine length?


Suggestions?

 

[Aaron Baker]

https://youtu.be/vPLN0ypi2Do

I just uploaded this video to Youtube. I don't have a 16" carbine in 300 AAC/BLK to compare. However, I do have this 6.5" barreled SBR in 300 AAC/BLK. The suppressor in this video is a Thompson Machine ISIS-2 9mm. (Fixed barrel 5/8-24 mount.)

I don't know how loud your 8.5" gun is or what suppressor you're running, but this is definitely hearing safe for me.

You'll notice that the gun doesn't cycle fully. It does eject the spent cartridge, so I'm getting all of the same ejection port noise that you'd be getting with your gun. (In other words, despite the gas problems, it's not any quieter because it's operating as a single shot.) The only reason it doesn't cycle is that the 6.5" barrel is simply too short for factory subsonic loads (or my handloads, so far) to cycle. It's a problem of dwell time, and I haven't been able to tune the buffer and spring enough to compensate and get reliable stripping of the new cartridge. (Custom length gas would also solve the problem, as would, possibly, using a 30 caliber can that created more backpressure.)

Aaron

 

[Bartholomew Roberts]

Shooting my subs through my 9" upper, it is about as loud as a nailgun. The only thing I've got that is quieter is my suppressed .22LR.

 

[HRnightmare]

Good to hear. psa had 8" 300blk barrels on sale for $79 over the weekend. I picked it up just in case I have build something our of it.

 

[Bartholomew Roberts]

I'd also note my .300 sounds louder when I am shooting it (you hear the action noise better and the recoil spring) than it does when I'm letting someone else shoot it.

 

[taliv]

mine may not be apples to apples comparison, because it's a bolt gun with integrally suppressed barrel. but the barrel itself is about 8" inside there

it's pretty dang quiet.

 

[Crawfish1]

When I shoot mine it doesn't sound like it's going super sonic "no crack per say" but the noise is loud enough to echo in the forest. I have tried Remington 220 Gr subsonic with about the same report as my hand loads with IMR 4198



I wonder if I am over powdered for the length of the barrel and that's where the blast is coming from. Less powder for a shorter length barrel?

Does that make sense?

I wish I had a chronograph. I am using an Octane can. On the 16" barrel it's less than half as loud. I am sure both are staying subsonic.

Does 7.5" of barrel make that much of a difference in report?

My suppressed .40 M and P 4.25" barrel is way quieter.


Is there a better choice of quiet powder's outside of Acc 1680 / Imr 4198 for pistol length barrels ?

I know on my .22's the rifle shooting subs vs pistol is much quieter. But the pistols still are quiet enough to begin with.

 

[Crawfish1]

Taliv,


That's a cool looking setup.



Aaron,


Yours is way quieter than mine. I wonder what it would sound like when it had enough charge to completely cycle.


Bartholomew Roberts,

The noise I am getting is more muzzle blast than action noise. I use my can on a bunch of other things and it tames them well. It's just this one weapon that is troublesome for noise.


Hopefully I can figure it out.

 

[Aaron Baker]

Yours is way quieter than mine. I wonder what it would sound like when it had enough charge to completely cycle.

It would sound supersonic, which this can isn't rated for.

My gun's problem is that its gas system doesn't function well with factory subs. I've shot a number of different brands of factory subsonics through it, as well as handloads. None of them cycle. It only cycles with supersonic loads.

And factory subs are going to be somewhere just south of the speed of sound--far enough that temperature and slight manufacturing variances won't make a ton of them go supersonic, but high enough to get the best velocities they can with subsonic loads. So adding enough powder to make my rifle cycle reliably would turn the loads from subsonic to supersonic.

Maybe it's your can? I don't have enough experience to say anything negative about the Octane, but some cans are better on pistol calibers than rifle calibers because of the design of the baffles.

IMR 4198 (I assume that's the powder you actually meant) is fine for subs--I use it for loading .458 SOCOM. I think AA 1680 is the preferred powder for 300 AAC subs. If those are what you're using, your loads are probably fine.

At the end of the day, a longer barrel with the same loads and can will be quieter. That's just how it is. But you should be hearing safe with a 8.5" barrel, I'd think. Sorry I don't have any better answers.

Aaron

 

[redbullitt]

My 300 blk ar15 carbine had a 16 inch barrel before SBR. It has a 10 inch now. Suppressor is a surefire 7.62k. AA1680 powder, 220 smk at 1025FPS.

16 inch barrel is noticeably quieter, I would almost say very quiet compared to the SBR configuration. FWIW I like the SBR better in the AR, but if it were a bolt rifle I would keep it at 16 so it is quieter.

 

[Crawfish1]

Aaron,


Your right I meant to type 4198 not the other. Just loaded another 50 for testing purposes.

 

[Lennyjoe]

My 16" .300 Blackout is very quiet with the AAC Cyclone suppressor and 10.5gr of 1680 under 208 gr Hornady BTHP.

I just submitted my Form 1 for a SBR and will put a 10" (or shorter) barrel on it and see what she sounds like. But, I have quite a wait until I can give it a try.

 

[txblackout]

I have a specwar 762 on a 8.5" (or whatever it is) noveske. It isnt nearly as quiet as my ruger american bolt in 300 blackout.

I was somewhat disappointed in how loud it is, but as others have mentioned

1) being in an open space helps
2) not being the shooter helps
3) supposedly switching buffers and springs can help a lot.

The bolt gun is extremely quiet so it is the gas system that makes a ton of noise which I dont think the suppressor can help with.

 

[Crawfish1]

Shot my 8.5" again today decided it was too loud and now it's time to sell it and try something else. Too bad I really liked the feel and looks of it.

 

[redbullitt]

Yeah it is definitely a trade off. Handy rifle, but louder than the longer barreled version. Makes one heck of a house gun with super sonics though I think.

Consider getting a bolt or break action with a longer barrel for the quiet work. I think you would be more than happy there. My bolt whisper when shot wet is very quiet, especially if I use light bullets and fast powders.