Is a 9mm Carbine less "loud" than a pistol?

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Orion8472

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So, the title pretty much says it all. If you're using the same ammunition, how much less "bang" do your ears perceive from a 16" carbine over a handgun?
 
All of this is contingent upon a person wearing the required hearing protection. But I was wanting to know if the carbine [Ruger PC Carbine, for example] will be less loud than a pistol. I'm about to the place where I won't be shooting 9mm, unless a carbine produces less of a blast to the shooter.
 
Of course, both require hearing protection. I can't quantify how much less "bang", but my 16" carbine does seem less loud, than say a 5" pistol with the same ammo. Makes sense to me, since the carbine muzzle is further from my ears....
 
Noise is probably a little louder in a pistol, but not enough percievable difference if niether are surpressed.
 
I can attest first hand that my AR9 10.5" pistol is noticeably different (less) than either my G17 or G26.

All require ear pro.
 

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Pressure at bullet exit is what makes the discharge sound.

In a longer barrel, the gases have to expand to fill a larger volume. Same amount of gas but more volume (longer barrel) means less pressure.

Because the pressure will be lower at bullet exit in a longer barrel, the noise will be less. How much less depends on a lot of things.

I know that .45ACP isn't 9mm, but they are both pistol cartridges. Here's some noise data showing that a Thompson has a discharge level of 151dB while a 1911 with its much shorter barrel has a discharge level of 159dB. That equates to a sound power reduction of more than a factor of 6 in the longer barrel.

https://www.caohc.org/UserFiles/file/Shot of Prevention extra handout.pdf

The data also shows sound power levels for .22LR from both rifles and pistols and the rifles are significantly quieter.
 
The simplest answer is ‘no.’ Sound is generated by the sudden release of high pressure gases at the muzzle at the moment of bullet exit, The higher the pressure the older the bang. The exception to that is a barrel length that is too long to achieve maximum powder burn and therefore presume at bullet exit. So the shorter barrel of a pistol would produce less Dbs than the loner barrel of a carbine. That said understand that the difference between the two guns would not be distinguished by human hearing. A 9mm round at standard pressure will produce an average Db rating of 159. Firing +P and +P+ will be higher than standard pressure. The Db level will vary with barrel length, but it could only be measured by a proper measuring device. I learned the above by reading about suppressor design. As I wrote at the start of this post: Sound is generated by the sudden release of high pressure gases at the muzzle at the moment of bullet exit,
 
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The simplest answer is ‘no.’ Sound is generated by the sudden release of high pressure gases at the muzzle at the moment of bullet exit, The higher the pressure the older the bang. The exception to that is a barrel length that is too long to achieve maximum powder burn and therefore presume at bullet exit. So the shorter barrel of a pistol would produce less Dbs than the loner barrel of a carbine. That said understand that the difference between the two guns would not be distinguished by human hearing. A 9mm round at standard pressure will produce an average Db rating of 159. Firing +P and +P+ will be higher than standard pressure. The Db level will vary with barrel length, but it could only be measured by a proper measuring device. I learned the above by reading about suppressor design. As I wrote at the start of this post: Sound is generated by the sudden release of high pressure gases at the muzzle at the moment of bullet exit,
I agree with all of this except one thing: My own chronograph tests prove that that exact same round fired in my pistol is about 200fps slower than from my carbine. Therefore the pressure in the carbine must be reaching higher levels because pressure IS directly related to velocity.
 
Therefore the pressure in the carbine must be reaching higher levels because pressure IS directly related to velocity.

The pressure has more time to cause the bullet to accelerate in the longer barrel. It isn't necessarily more pressure. Once the bullet exits the muzzle it won't continue to accelerate. And in rare cases with long barrels and light powder charges the bullet can start to slow down while still in the barrel. This happens in 22 rifles with quite long barrels.
 
So, the title pretty much says it all. If you're using the same ammunition, how much less "bang" do your ears perceive from a 16" carbine over a handgun?
Yes, assuming the same ammo is being used, the longer barrel will be quieter. MP5 is quieter than a Glock 19. Heck, my .44 magnum rifle with 20" barrel is quieter than a .22 pistol with 3 inch barrel.
 
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I agree with all of this except one thing: My own chronograph tests prove that that exact same round fired in my pistol is about 200fps slower than from my carbine. Therefore the pressure in the carbine must be reaching higher levels because pressure IS directly related to velocity.

Actually we agree. Higher velocity = higher pressure. My point was your hearing will not notice the difference. Hearing protection is necessary no matter what the barrel length of a 9mm gun.
 
I have a 16" 9mm and I would say its about 1/3 less loud than a 5". Not scientific, but thats what it seems.

i would say the 9mm is about 1/2 way between a 5" pistol and a 22LR rifle. It is quieter than a .22lr pistol.
 
Therefore the pressure in the carbine must be reaching higher levels because pressure IS directly related to velocity.
You can find pressure curves that show definitively that the pressure drops as the bullet moves down the barrel.

There are several at this website.
https://www.frfrogspad.com/intballi.htm

There's an initial peak that happens very early in bullet travel, then from there on, the pressure drops continually until the bullet exits.

However, even though it is lower by the time the bullet exits from the barrel, it is still significant enough that the push it creates on the back of the bullet is also significant. Even though it's dropping as the bullet moves down the barrel, it's still exerting enough force to keep accelerating the bullet.

From one of the pressure plots on the linked website, it can be seen that the chamber pressure in that particular case is still over 10,000psi at bullet exit. That's still going to be pushing on the bullet with a lot of force, even if it's not as much force as it was earlier.

Think of as pushing a heavy cart. At the beginning, you have to push very hard, then as it gets rolling, you can stop pushing quite as hard, but even so, you can keep it speeding up even by pushing with less force than you used at the beginning to get it started. The longer you push, the faster it goes, even if you're not pushing as hard at the end as you were at the beginning.
 
...how much less "bang" do your ears perceive from a 16" carbine over a handgun?
That's a difficult question to answer. Supposedly the human ear can distinguish between the sound power of noises that differ by as little as 1dB.

HOWEVER, at some point, noises become so loud that they really aren't perceived as noises at all. I forgot my hearing protection and fired a rifle at a covered position one time years ago and the discharge noise was reflected off the roof and felt like something tapped me on my head. I honestly didn't realize what was going on for a minute, then figured out that I didn't have my hearing protection on.

Similarly, I had the great misfortune to fire a .357Mag in an enclosed space on one occasion without hearing protection and it was so loud I didn't hear it at all as a sound. I just went nearly totally deaf instantly and stayed that way for awhile.
 
Thanks for all the replies.

I was just wondering if, with 9mm, it's the same as it is with 22lr. I have a 22lr pistol that is definitely louder than my 22lr rifles. And I have fired 38 Special out of a top load 1851 revolver and it was FAR louder to me than the same load out of my 1873 Taylors with 20" barrel.

So, I would hoping that a PC Carbine, with the 16" barrel, would be enough of a difference to where I could still keep the 9mm I have when I get rid of my pistols.
 
Interesting thread here. I own a 9mm PC Carbine and three 9 mm handguns and have never noticed any difference. But then I'm always wearing hearing protection whenever any of them are fired. One of these days I'm gonna fire them one after another with hearing protection and see if I can notice any difference. Could be interesting.
 
Friend of mine has a small range out back where we shoot mostly 22's rifles & various handguns. I have a couple trail cams out in his woods. When I go out there this week to swap SD cards on the trail cams I should bring the Glock G19 and the Ruger PC Carbine. Then we can have two sets of ears listening. I'm also getting curious about this.
 
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