How much more can I expect from this? (300 BO)

[fester225]

I just finished my first attempt at a suppressor for 300 Blackout. (1.5" x 14" with baffles approximately every 3/4"). It is performing at the level of 14dB suppression. I was hoping for more.

My baffles are open to 0.330". Is this too big?

[fishman]

My baffles have a .375" bore and they're very quiet.

What kind of baffles?

[fester225]

Flat SS washers with a large ball bearing pushed in about 1/4", which expands the center hole to about 0.330" dia.

How much suppression are you getting from yours?

[fishman]

I don't have a meter but it sounds like between a 22LR and a .177 pellet gun, closer to the pellet gun. Mine is 1.625"x11" machined k baffles.

Clipping your baffles might help you.

[Matt in TN]

How are you measuring your sound pressure levels? It takes pretty sophisticated equipment to accurately measure things like gunshots.

You may be doing better than you think.

[fester225]

The sound level is being measured with a dB meter on the fast setting. Being careful to use consistent test conditions, I went from 117dB (bare barrel) to 103dB (with suppressor).

As a relevance check, I did the last measured test with bare ears. My ears say 103dB is too loud.

[T-Rex]

103db is a VERY comfortable gunshot.
117db would be an awesome number for suppressed 300blk, but you're metering that from unsuppressed?

You're using incorrect, insufficient, or poorly calibrated equipment. Care to share your specs?

[yondering]

The sound level is being measured with a dB meter on the fast setting. Being careful to use consistent test conditions, I went from 117dB (bare barrel) to 103dB (with suppressor).

As a relevance check, I did the last measured test with bare ears. My ears say 103dB is too loud.

You're probably using a smartphone app, aren't you? Ignore that stupid junk, they don't work for gunshots. Your bare muzzle reading should have told you it wasn't working right.

What kind of performance were you expecting from a flat washer baffle stack? There is a reason pretty much everybody uses more intricate baffles.

[CMV]

I just finished my first attempt at a suppressor for 300 Blackout. (1.5" x 14" with baffles approximately every 3/4"). It is performing at the level of 14dB suppression. I was hoping for more.

My baffles are open to 0.330". Is this too big?

0.330" for .308" projectile and not precision machined? From baffle construction description one would assume something along the lines of PVC or threaded pipe & caps for the remainder. You have a recipe for disaster. Sounds like you're fortunate that suppression sucked was the only issue.

I hope you're not in the US & wasted a $200 stamp for such nonsense.

300 BLK is not difficult to suppress to Hollywood quiet. A very simple build if you are machining it, and even simpler with a DIY felony kit from SDTA et. al. Stay out of Home Depot & do some reading here on the multitude of ways we have done home builds to get 300BLK Hollywood.

[willy1947]

I just put together an AR pistol 10.5 barrel. I have a Specwar 7,62, So I tried it, I shot it in a bank 6ft away. I heard the 220gr bullet hit and the action work. Lots of white smoke, not much else.

[a_canadian]

Since you've built it already, I'd suggest forming cross-bore jetting features into those SS washers. Make a simple jig to support the domed washers securely, then whack them with a punch on one edge of the hole until that edge is about opposite to the main domed shape. You'll need to carve your supporting form such that the whole thing doesn't collapse under the hammering, just the one small area you're hitting. I would expect significant improvement with that more complex face profile, directing the gas flow across the bore.

As for dB meters, yeah, not all that great. My SPL meter gives me about 128dB from a 4" barrel with CCI SV. 22lr. Between about 103dB and 107dB with a K baffle can depending on the environment where I'm measuring. Obviously neither is correct, but useful for comparison to other things.

[fester225]

As for dB meters, yeah, not all that great. My SPL meter gives me about 128dB from a 4" barrel with CCI SV. 22lr. Between about 103dB and 107dB with a K baffle can depending on the environment where I'm measuring. Obviously neither is correct, but useful for comparison to other things.

Some who understands the concept of useful comparison!

In addition, you made a useful suggestion! What is this board coming to?

[a_canadian]

It's okay, no need for panic. Someone will come along soon enough and spank me for spreading incorrect information. I'm getting used to it.

[yondering]

No spanking, but if you know both numbers are wrong, why do you think they are valid for comparison? You're assuming both are equally wrong so that the difference between them is valid, but that is most likely not correct either.

Guys, do some research on these sound meter apps. The microphones on your smart phones can only measure up to ~95 Db; the apps are just estimating the noise level above that, with algorithms designed for more sustained noises than gunshots.

[a_canadian]

Wasn't talking about a smartphone app. Tried that years ago, saw the numbers were ridiculous, so I bought a dedicated SPL meter. Cheap but surprisingly consistent and delivering numbers which confirm my auditory impressions of differences between ammunition types and suppressor baffle changes. The value displayed by my meter diminishes as the sound pressure goes higher, so there's a compression to be accounted for if attempting to compare to proper mice and meters. But I don't try to compare directly. There's no point. I compare to my own records, and for that purpose such a meter is quite consistent and useful when developing better baffles.

[fester225]

Guys, do some research on these sound meter apps. The microphones on your smart phones can only measure up to ~95 Db; the apps are just estimating the noise level above that, with algorithms designed for more sustained noises than gunshots.

Neither I nor a_canadian said anything about using a smartphone app to measure sound levels. That was yondering. I'd give the make and model of the meter I was using, but on this forum it would get shot down if it was being done by the NIST.

a-canadian: Let me know if you think of anything else.

[a_canadian]

Well you might want to drill a small port in your first baffle, about halfway between bore edge and tube. Say 1/16"? You can always go bigger later if that doesn't seem to make a positive change. And perhaps don't do the reversed bend in that first one - a lot of makers feel that the first and last baffles ought to be symmetrical in the name of stability. The little hole is called a 'Dater' hole after its most well known promoter, a small pressure relief which both reduces risk of first round pop (more of a concern with subsonic rounds) by dropping initial pressure and temperature in the blast volume, reducing potential for oxygen combustion, while also reducing strain on that initial baffle by helping dump a bit more pressure into the second chamber.

[destrux]

As for dB meters, yeah, not all that great. My SPL meter gives me about 128dB from a 4" barrel with CCI SV. 22lr. Between about 103dB and 107dB with a K baffle can depending on the environment where I'm measuring. Obviously neither is correct, but useful for comparison to other things.

Some who understands the concept of useful comparison!

In addition, you made a useful suggestion! What is this board coming to?

The meter you're using isn't able to capture spikes and meter all frequencies with the same accuracy, so simply changing the tone or duration of the sound without reducing the decibels would show up as a different decibel reading. That's typical characteristics of low cost meters (low cost being under $5000). That doesn't provide useful comparison it provides a wild goose chase. I've tried this myself using a meter that is typically used for stereo competitions and cost $1,400 and readings varied several decibels just from changing where I stood on the shooting range.

[fester225]

I've tried this myself using a meter that is typically used for stereo competitions and cost $1,400 and readings varied several decibels just from changing where I stood on the shooting range.

I would EXPECT meter readings to change just by changing where you stand.

[fishman]

I've tried this myself using a meter that is typically used for stereo competitions and cost $1,400 and readings varied several decibels just from changing where I stood on the shooting range.

I would EXPECT meter readings to change just by changing where you stand.

yeah, thats kind of how sound pressures work. the closer you are to something, the louder it is.

[a_canadian]

... which is why I always metre in two particular locations, each with different acoustical characteristics, then take an average between these series of readings. My results are quite consistent, and change significantly depending on ammunition brand or changes in baffle configuration. Since in many hundreds of rounds tested the numbers have been consistent, and since the metered results confirm my auditory impressions of quieter or louder shots per changes in ammunition or baffle setups, I see no reason to throw out the meter. It has served me well, if not delivering numbers which are directly useful for comparison to a properly calibrated $10,000 meter. Frankly if my ears tell me scan is quieter and the meter backs up that impression, it's done the job well enough for my use. But go ahead, be a meter snob and spend your thousands of dollars for metering F1 cans. Makes sense to you I guess... to me that's money I could spend more usefully in a few thousand other directions.

[hardcase]

The sound level is being measured with a dB meter on the fast setting. Being careful to use consistent test conditions, I went from 117dB (bare barrel) to 103dB (with suppressor).

As a relevance check, I did the last measured test with bare ears. My ears say 103dB is too loud.

Assuming these are sub-sonic loads, what I do is measure the fps instead of the dB using a chronograph. Supers are noticeably louder as they have a sonic crack. If I were you I'd make sure your loads are sub-sonic first.

From what I've read, as a point of reference, a passing 18 wheeler on the Interstate has a dB of about 110 dB. I'd think you dB meter is faulty.

[fester225]

Assuming these are sub-sonic loads, what I do is measure the fps instead of the dB using a chronograph. Supers are noticeably louder as they have a sonic crack. If I were you I'd make sure your loads are sub-sonic first.

From what I've read, as a point of reference, a passing 18 wheeler on the Interstate has a dB of about 110 dB. I'd think you dB meter is faulty.

AT LAST! Somebody asks what kind of load I was firing! (208gr sub-sonic)

Like a_canadian was saying, it's all relative. It also doesn't matter what the numbers are if I think the result is too loud. I think it's too loud, so I'm looking for improvement.

[andromax]

Curious what the accuracy is like. That's a pretty tight bore especially for non precision work.

60* cones are a good start for an improvement.