Quietest 300 BLK Subsonic Round for Daniel Defense M4 ISR

Discussion about rifles in 300 AAC BLACKOUT (7.62x35mm), hosted by the creator of the cartridge.

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Freedom1973
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Re: Quietest 300 BLK Subsonic Round for Daniel Defense M4 ISR

Post by Freedom1973 » Mon Oct 01, 2018 4:52 pm

dellet wrote:
bangbangping wrote:
dellet wrote:There are heat sensing detectors and other ways for fire warning and control.
Should be an easy matter to run ventilation when he digs the 100 yard tunnel.
Can't wait to read about this one in the papers

Police mistakenly shoot home owner.

mxjoe was was shot by police emerging from an underground tunnel wearing a gas mask, earmuffs and carrying an assault rifle.

It seems that the fire department was dispatched to a monitored fire alarm signal. Upon arrival, muffled shots were heard coming from the homeowners basement, prompting the fire department to call the police, who in turn called the SWAT team.

The unfortunate incident is under investigation. It appears that the SWAT team had made repeated attempts to gain the attention of mxjoe with a loud speaker, but he was unable to hear them because he was in a sound proof, home constructed shooting range.

mxjoe, who was un-aware of police presence, exited his shooting tunnel after it filled with tear gas fired in by the officers and was shot upon his hasty exit. The officers defended their actions by stating that "seeing an armed man with a gas mask rush from the building was considered a threat to their safety".

The statement from mxjoe offered a different version. "here I was minding my own business, shooting in the basement, when an exhaust fan apparently failed. I was trying a new powder that produces a lot of smoke and gas so thought nothing of it. I just put on my mask and kept testing. All of a sudden, the smoke became unbearable, so I decided to get some fresh air. The room is sound proof so I don't bother the neighbors, I had no idea the police and fire departments were out there. Maybe they should have sent in a remote or something first, before the gas"

It seems the whole mix-up has something to do with a dead battery in a smoke detector. According to mxjoe "the damn smoke detector had been chirping for months and not working. It seems that my wife got tired of hearing it and replaced the battery. I guess it works fine now."

Mrs mxjoe was not available for comment.
So Dellet are you volunteering to be the tunnel lookout so you can use the tunnel range? If not I might volunteer. :lol:
Not really...but I could totally see the scenario playing out.
Wishing I had more land...

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mxjoe35
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Re: Quietest 300 BLK Subsonic Round for Daniel Defense M4 ISR

Post by mxjoe35 » Mon Oct 15, 2018 1:22 pm

So my wife left me alone in the house again and I was able to get a little more test data. I tested LilGun vs H110 with the same bullet and powder weight. I then tested LilGun same powder weight with different bullet weights. Results aren't shocking, but interesting. H110 runs about 125fps slower than the LilGun, and DB's are almost identical. Test 2 running 8.5 grains of LilGun I tested a 165gr bullet and a 150gr bullet. I gained about 15fps with the 150gr and the sound dropped only a half of a DB. I have some more testing to do, just have to wait for my wife to leave me alone again! LOL

https://www.pdfhost.net/index.php?Actio ... 35aca0e862

Suputin221
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Re: Quietest 300 BLK Subsonic Round for Daniel Defense M4 ISR

Post by Suputin221 » Wed Nov 21, 2018 8:09 pm

mxjoe35 wrote:So my helper insisted that because she helped me build my bench ( handed me screws), she got to be in the picture! :lol: I am getting my chrono next week. I also bought a db meter, so there will be no guessing which is the quietest. Hopefully next weekend I'll get to do some testing.
Unless you spent several thousands of dollars on that dB meter you have wasted your money and will be doing nothing but guessing.

The problem with inexpensive and unsuitable sound meters is that they do not react fast enough to be able to capture all of the sound event. That means they miss the peak and will show the noise to be much quieter than it really is.

A cheap (unsuitable) sound meter is the equivalent of trying to measure the top speed of a Ferrari with a bicycle speedometer. How can you possibly know which engine mods make the car faster when the speedo can't measure the top speed of the car?

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John A.
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Re: Quietest 300 BLK Subsonic Round for Daniel Defense M4 ISR

Post by John A. » Wed Nov 21, 2018 8:30 pm

I've been designing and building suppressors for a long time now. But even though I consider myself much more than a "hobbyist", I'm not sinking thousands of dollars into a db meter and microphones.

I guess I would as a business expense that I could claim on my taxes if I were to get my manufacturer license.

But while I do understand what you mean about cheap db meters not being as accurate, they serve me well enough to discern which is more quiet, or more loud than another silencer.

Same for while testing ammo's and powders and such.
When those totally ignorant of firearms make laws, you end up with totally ignorant firearm laws.

Suputin221
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Re: Quietest 300 BLK Subsonic Round for Daniel Defense M4 ISR

Post by Suputin221 » Wed Nov 21, 2018 8:30 pm

mxjoe35 wrote:Test Data: https://www.pdfhost.net/index.php?Actio ... bd37a37d83

Hope this link works.
Notice how there is only a 4dB difference between suppressed and unsuppressed? Thats because the meter is reacting too slowly and missing much of the sound peak.

FWIW I've metered subsonic loads using 9.0gr of Little Gun and got 132 dB in my 10" AR. Which suggests you are missing over 15dB of sound level. Keeping in mind that 3dB represents a doubling of sound energy and 10dB represents 10x as much sound energy.



mxjoe35 wrote:I have a smoke detector down there, it needs the battery changed. (keeps chirping at me) No sprinkler system. We shot approx 50 rds, didn't notice to much ...if any smoke. Maybe because my loads were so light!? But thanks for the tip, I will keep an eye on that.
You are aware that primers put vaporized lead into the air? In your basement that lead has nowhere to go. It will eventually settle only to be kicked up and circulated through the air overtime someone walks into the area. Shooting indoors just leads to everything in your house being contaminated with low levels of lead. A situation that is especially bad for young children.

Suputin221
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Re: Quietest 300 BLK Subsonic Round for Daniel Defense M4 ISR

Post by Suputin221 » Wed Nov 21, 2018 8:42 pm

John A. wrote:I've been designing and building suppressors for a long time now. But even though I consider myself much more than a "hobbyist", I'm not sinking thousands of dollars into a db meter and microphones.

I guess I would as a business expense that I could claim on my taxes if I were to get my manufacturer license.

But while I do understand what you mean about cheap db meters not being as accurate, they serve me well enough to discern which is more quiet, or more loud than another silencer.
A cheap sound meter simply cannot measure what you are attempting to measure. Therefore whatever data it produces is entirely worthless.

Silencers shorten the peak impulse of the muzzle blast, which makes the difference between reality and the sound meter number even greater because unsuitable meters simply cannot react fast enough.

The OP is reporting a 4dB difference between suppressed and unsuppressed, when the real value should be 25-30 dB depending on the suppressor. What he's not getting is that the meter is pegging on every shot, thus any changes he makes to the load are going to show the exact same measured value because the meter is just pegging. He thinks a half dB is making an improvement but the only way to get an actual number is an average of 10 shots. I've seen variation in a single load exceed 4-5 dB in a 10 shot average. Its a gigantic exercise in self deception and silliness.

A cheap sound meter is of no worth and cannot produce any data that serves of any use. Once again, its like trying to measure the top speed of a Ferrari using a bicycle speedometer. Can't be done.

In the end its your money. Spend it how you wish. Just don't fool yourself into thinking that the data such an instrument produces is of any worth.

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John A.
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Re: Quietest 300 BLK Subsonic Round for Daniel Defense M4 ISR

Post by John A. » Wed Nov 21, 2018 9:13 pm

If I shoot 3 shots each of two different loads back to back, the meter will tell me if there is one more quiet than another.

Will it be as accurate as a $5000 meter and mic and stuff?

Nope.

If your meter is rated at 130 or 135db peak, shouldn't max out if the sound is less.

I say shouldn't, but I do realize what you're saying too and don't necessarily disagree with you, but since I don't require anything more than knowing if one is more quiet than another if my ear cannot discern a difference is mostly a moot point anyway.

If my ear can tell a difference, and a cheap meter can tell a difference, that's good enough for me. I don't have to know any more than that. I would never say that my rimfire cans meter down into the low 100's with a straight face, but if I get 110 with one type of bullet and 118 with another and the 118's also sounded louder to my ears, that's all I concern myself with. I don't necessarily need to impress anyone with a low number.
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Re: Quietest 300 BLK Subsonic Round for Daniel Defense M4 ISR

Post by Suputin221 » Sun Dec 23, 2018 8:05 pm

One problem ..... or not .... depending on how you view it is that your ears can lead you astray quite easily. Our ears can be fooled by both duration and frequency. Longer duration and higher frequency will both be perceived as being louder.

I learned this early on when I was developing baffle designs. I ended up with what I thought was a pretty quiet design based upon ultrasonic principles. I was greatly disappointed when we put this can on Al Paulson's meter and it showed up as being quite loud. It also made a very unpleasant high pitched noise.

Another experience I learned from was the difference between a 9mm SMG can and a 45ACP SMG can. To me and everyone I asked, the 45 can seemed quieter. However the sound meter showed the 9mm can to be 10 dB quieter. This was almost completely a factor of the frequency mix of each muzzle signature. The 45 made a nice low frequency "thump" while the 9mm was much high frequency "crack" kind of noise. Both of these were with subsonic ammo so no supersonic flight noise. 10 dB is not an insignificant difference.

The last experience I will related was when we were testing 22 rimfire cans on a pistol. With each shot, Al would call out the SPL so I had the opportunity to compare actual sound level with my perception of the shot. Quickly I realized that what the sound meter read and what I heard were very different things because we were experiencing them from different locations. When the meter said a shot was very quiet, I often experienced it as being louder while some of what I thought were very quiet rounds, the meter said were much louder.

AFAIK this is the difference between back pressure and maybe a few other factors that result in changing amounts of muzzle pressure vs ejection port pressure or pop. The point of this being you need to decide what you want to be quiet, for the shooter or at the muzzle? Because they aren't the same thing.

If you are going for perceived noise, put the meter down, it won't help you. If you want actual sound reduction, an insufficient meter won't help you either. The meter is simply not picking up enough of the sound event to be of any use.

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Re: Quietest 300 BLK Subsonic Round for Daniel Defense M4 ISR

Post by Dolomite_Supafly » Tue Jan 01, 2019 11:39 pm

I use a laptop with recording software to compare loads. The key to making it work is the microphone. The laptop as well as most "computer" nice just can't handle it. I was given a VERY expensive microphone and it makes it possible to compare loads. I cannot get a measurement in decibels but I can accurately compare different loads.

I tried with just the laptop microphone and it was wildly inaccurate. With a cheap microphone I got similar results.
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