Question about comparative noise


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19-3Ben
February 24, 2012, 11:16 AM
So, I'm thinking long term here. I'm nowhere near being able to afford it at this point, but I'd like to get a CX4 storm. I know PCCs aren't for everyone, but for my purposes and desires, I like them.

I would consider either the .40 or the 9mm. I would consider getting the barrel shortened (i know, i'd have to get an SBR), and threaded for suppressor.
So the question comes in, which would likely be quieter, the 9mm with heavy bullets (147gr or similar), or .40 with heavy bullets (180gr. or similar)?

Also, looking at ballistics by the inch, it looks like a 180gr. .40cal load from a 14-16" bbl is going to hit 1100+ FPS anyway, so is it going to be supersonic and make a ton of noise anyway?
It looks like the 147gr. 9mm would be running just a hair under 1100fps.
So is there going to be any difference in sound signature? will a suppressor help reduce sound?

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CoRoMo
February 24, 2012, 11:55 AM
I've always read/heard that generally, the smaller caliber projectile can be suppressed more so than the larger.
will a suppressor help reduce sound?
I can't give you a big enough 'YES' to that answer.

A suppressed pistol caliber SBR makes for a near perfect HD weapon in my book.

19-3Ben
February 24, 2012, 12:08 PM
A suppressed pistol caliber SBR makes for a near perfect HD weapon in my book.

Which is exactly the use I have in mind for it.
Thanks so much for the advice.

I can't wait to wade into the mire of figuring out which suppressor to use. I feel like that's going to be an education all in itself.

RhinoDefense
February 24, 2012, 12:18 PM
Suppressor will reduce the sound of the gunshot. If the bullet stays subsonic the sound will be the quietest. A suppressor will still work with supersonic ammunition, it just won't be as quiet as it could be. For home defense, I wouldn't be concerned with getting the quietest shot from your weapon. Put the suppressor on it and use the best ammunition that will function reliably in the weapon. The suppressed shot will certainly be better than an unsuppressed shot. Guns being shot in homes are really loud and the damage is more than being outside because the sound bounces off the walls and is heard again (remember sound is in waves). If you have a supersonic suppressed gunshot, it's still going to be loud enough to cause permanent hearing damage, although not as much as completely unsuppressed. If you touch off some rounds in a house, regardless of what ammunition you use, you'll be glad you have a suppressor on your weapon.

Greg528iT
February 24, 2012, 01:57 PM
I like what I read yesterday about suppressing a 45 acp. The original thought was, being a subsonic round, it'd lend itself well to supression.

The 45 is a big hole to try and keep the sound in.

Wouldn't it then follow that, a 45 MAKES a big d.m hole in the intruder????

19-3Ben
February 24, 2012, 09:37 PM
I've always read/heard that generally, the smaller caliber projectile can be suppressed more so than the larger.

The 45 is a big hole to try and keep the sound in.

Ok, so what I'm seeing as the pattern here is that a 9mm would be quieter suppressed than a .40?
So then the next question is, how much quieter?
And yes, I'm speaking in terms of generalities and apples to apples comparisons. I realize there will be statistical outliers on either side.

Greg528iT
February 24, 2012, 10:47 PM
Google, suppressor results. I've looked before, saw maybe 5-10 db differential,

19-3Ben
February 25, 2012, 09:15 AM
Thanks again for the help. I'm no noob to guns, but the amount that I know about suppressors and for that matter, most NFA stuff, could be poured into a shot glass and still have room to spare!

Telekinesis
June 28, 2012, 11:51 PM
A 9mm 147gr bullet (including most high quality defensive ammo) will be safely subsonic in a pistol with a 4-5" barrel, but depending on how long your barrel is on your SBR, it might end up getting close to being transonic. However, it will be easier to get a 9mm to be subsonic than a .40. I'm not aware of subsonic defensive ammo in .40 when fired from a pistol, so I doubt that it would be subsonic when fired from a SBR.

The difference between a supersonic and a subsonic round is definitely noticeable when firing suppressed weapons. To get an idea of what it sounds like, look up some youtube videos of a suppressed AR 15 (almost always supersonic) and a suppressed 9mm pistol (almost always subsonic). Its not a direct correlation to a 9mm vs .40 comparison, but it will give you a place to start. Supersonic ammo is still pretty loud if you're firing it indoors. So yes, 9mm will generally be quieter than .40.

A good place for suppressor test data is NFAtalk.com. They have a good bit of data on different suppressors. From what I've seen, a good 9mm suppressor will meter in the 125-129db, and a .40 suppressor will be around 135-140db. Hearing safe is considered 140db.

You might also want to look into a 9mm AR SBR. It would let you get the suppressor underneath the handguards which means a much shorter overall length. I hear that they are pretty quiet too.


Wouldn't it then follow that, a 45 MAKES a big d.m hole in the intruder????
It's only 2.5mm wider than a 9mm. Not quite a "big d.m hole" in my opinion :neener:

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