Looking for a Subsonic Carbine for pest control
- Thread starter SkydiverChris
- Start date
Id doubt the boat tail would make a difference. It's possible there could be a difference between round nose and spitzer. Not sure how much noise difference that would make?
digitalblue
CGN Regular
- Location
- GTA unfortunately
I do a lot of shooting on noise sensitive properties and I've learned a few things.
Subsonic loads only mitigate bullet noise (ie. supersonic crack), the limiting factor to how "quiet" a rifle is in controlling the muzzle blast.
So-called "subsonic" cartridges like 300 Blk rely on a suppressor to eliminate the muzzle blast. These subsonic loadings are still incredibly loud when fired without a suppressor.
Your only means to reduce muzzle blast without a supresor is by controlling the volume of gas generated and the gas pressure at the muzzle.
This is easily realized with something like 38spl (very low pressure cartridge) in a rifle length barrel, the fast pistol powder minimizes gas volume generated and the long barrel serves as an expansion chamber to lower the muzzle gas exit pressure and velocity.
While you can down-load a 300blk with small amounts of high speed pistol powder (ie Titegroup or Red Dot) to achieve similar results, you'll encounter issues with load density (since you're severely under filling a large case to avoid blowing up the gun with high speed powders) which compounds into erratic ignition without the use of fillers.
Long story short, a low pressure pistol caliber rifle is the easiest off-the-shelf solution for quiet shooting unless you can legally use a supressor.
Subsonic loads only mitigate bullet noise (ie. supersonic crack), the limiting factor to how "quiet" a rifle is in controlling the muzzle blast.
So-called "subsonic" cartridges like 300 Blk rely on a suppressor to eliminate the muzzle blast. These subsonic loadings are still incredibly loud when fired without a suppressor.
Your only means to reduce muzzle blast without a supresor is by controlling the volume of gas generated and the gas pressure at the muzzle.
This is easily realized with something like 38spl (very low pressure cartridge) in a rifle length barrel, the fast pistol powder minimizes gas volume generated and the long barrel serves as an expansion chamber to lower the muzzle gas exit pressure and velocity.
While you can down-load a 300blk with small amounts of high speed pistol powder (ie Titegroup or Red Dot) to achieve similar results, you'll encounter issues with load density (since you're severely under filling a large case to avoid blowing up the gun with high speed powders) which compounds into erratic ignition without the use of fillers.
Long story short, a low pressure pistol caliber rifle is the easiest off-the-shelf solution for quiet shooting unless you can legally use a supressor.
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Ok Doc, please provide the calculations with various projectiles and powder load. I just didn’t know sonic transition is a constant no matter size. So in your reasoning a 30cal projectile and let’s say Concorde jet have same atmospheric distribution causing an equal sound to result.
Im just interested in the math. It sounds very fascinating. Oh, show your work
Im just interested in the math. It sounds very fascinating. Oh, show your work
Try Trailboss. It is the cure for all the downloading problems with rifle sized cases.
Where did this data come from?
What equipment was used to collect the data?
How far away from the bullet's path was the microphone situated?
The 308 and 300WM bullets are the same diameter and thus should be the same flight noise.
I was with Alan Paulson (author of Silencer History and Performance Vol 1 and 2) when he measured the flight noise of a .30 cal projectile at around 155 dB IIRC. The microphone was situated approximately 10 feet from the flight path.
The numbers came from establishing noise sate zone around work areas. I’m not trying to cause a stink. This is the data for all objects. It a physical law when you input the numbers you have predictable results. The location of the microphone would give you a sound relative to that location, depending on how far it was from the muzzle and not the sound that is created entirely dependent on the size and velocity of the object. Investigate ask some questions read some text books and you’ll find the real answers. Good luck to you, sir.
I found a similar chart for muzzle blast in dbs for Pistol caliber bullets. There is no free ride. Large caliber sub-sonic muzzle blast is about as loud as the sonic boom. There is no free lunch, as some of us mentioned, the muzzle blast gets louder, the larger the caliber; the whole article can be found here: https://earinc.com/gunfire-noise-level-reference-chart/
The article contains similar charts for CF rifle and Shotguns:
@SkydiverChris, stick with .22 RF.
Table-3-CENTERFIRE-PISTOL-DATA-2019-10-29.csv
| .25 ACP | 155.0 dB |
|---|---|
| .32 LONG | 152.4 dB |
| .32 ACP | 153.5 dB |
| .380 | 157.7 dB |
| 9mm | 159.8 dB |
| .38 S&W | 153.5 dB |
| .38 Spl | 156.3 dB |
| .357 Magnum | 164.3 dB |
| .41 Magnum | 163.2 dB |
| .44 Spl | 155.9 dB |
| .45 ACP | 157.0 dB |
| .45 COLT | 154.7 dB |
147gr 9mm from an 8in adapter (like the ones we sell) will stay subsonic and is "quiet" for a 9mm, but still definitely not hearing safe. Quite a bit louder than CCI standard velocity 22lr. Haven't done a db meter test but I think it's also louder than normal "high velocity" 1200-1300fps 22lr ammo out of an 18.5 barrel.
357 will be quite a bit louder yet than 9mm given the same adapter/shotgun setup. Will typically be supersonic out of an 8in adapter unless you go really heavy with the projectile weight or load it soft.
digitalblue
CGN Regular
- Location
- GTA unfortunately
Pistols are only loud because of the short barrel. But stick any of those pistol cartridges in a rifle length barrel and you'll find a substantial change in the tonality and loudness of the muzzle blast.
