Suppressors and first round pop


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SOT_II
September 1, 2004, 06:23 PM
This is an excellent example of first round pop when using a suppressor, the first round has a distinctly higher sound value...and the others are much quieter.

http://www-personal.umich.edu/~scoville/video/shooting/M16-22-supressed.mpg

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WhiteKnight
September 1, 2004, 06:55 PM
Is that an m16 with a Ciener conversion?

possenti
September 1, 2004, 07:58 PM
I don't understand - Why is the first round a little louder?

If our :cuss: government would let us own them without restrictions (like in the good ol' days), maybe I'd understand it.

SodiumBenzoate
September 1, 2004, 07:59 PM
Maybe because the gas that builds up helps to quiet the weapon?

boofus
September 1, 2004, 08:05 PM
I've heard it's because before the first round is fired the suppressor is full of oxygen. It all gets blown out or consumed in the first shot so the ones that follow aren't as loud.

Dunno whether that explanation is true or not. Never really noticed with my .45 suppressor, they all pretty much sound the same.

Hkmp5sd
September 1, 2004, 08:18 PM
The oxygen in the suppressor supports the combustion of any gunpowder that hasn't already been consumed due to lack of chemical oxygen in the powder. After the first round, the suppressor is full of gas.

WhiteKnight
September 1, 2004, 09:12 PM
How long does the gas in the suppressor last? In regard to bolt actions, would letting the rifle sit for a couple minutes while you change target/get a drink/reload/etc allow the oxygen to build back up/gas diminish?

SDC
September 1, 2004, 09:16 PM
The oxygen in the suppressor supports the combustion of any gunpowder that hasn't already been consumed due to lack of chemical oxygen in the powder. After the first round, the suppressor is full of gas.

This is the answer that makes the most sense; apparently, there have been experiments in which a suppressor is filled with inert gas (like CO2) prior to the first shot in order to AVOID that first-round "pop", but unless you happened to be doing a hit in the Kremlin, I can't imagine it would be worth the effort.

SOT_II
September 1, 2004, 10:32 PM
It just the ambiant air built up in the spaces in the suppressor. That littl evolume of air makes a "pop" the first time as it is pushed out and as there is a temp change in the suppressor.

El Tejon
September 1, 2004, 10:53 PM
So, uh, no one else still breathes in their suppressor?:uhoh: :D

You kids and your rocking and rapping and your baggy pants. Back in my day we breathed in our suppressors and we like it. I took the ferry from Shelbyville which in those days was called East Ogdenville. I tied an onion to my belt . . .:D

WhiteKnight
September 1, 2004, 11:01 PM
How long does it take the ambient air to build up?

SOT_II
September 1, 2004, 11:22 PM
El Tejon,

That was funny! Nothing like doing it old school....

SOT_II
September 1, 2004, 11:24 PM
Normally it's when you take the suppressor out for the first time each session...get a couple rounds though it and it starts heating up and the air is displaced by shooting...and it stays that way for a while.

As El T stated, a quick puff of air into the suppressor will diminish FRP pretty readily....it's really not that big of a deal...I just thought it was a good illustration of FRP...as many have not seen or heard it.


How long does it take the ambient air to build up?

Kenneth Lew
September 1, 2004, 11:43 PM
A liquid medium will usually displace some of the oxygen.

QuarterBoreGunner
September 1, 2004, 11:58 PM
A liquid medium will usually displace some of the oxygen.

Ok, so is this why some cans are advertised as 'wet capable' meaning you fill the baffles/wipes with a liquid (I've heard that a field expedient solution is urine... and what a picture THAT paints)? I'd always thought that it lowered the dB level overall but eliminating the 'first round pop' seems to make more sense.

mfree
September 2, 2004, 04:30 PM
Could it be that the initial air charge is cold and hence denser, and each successive shot is then though heated, thinner gasses?

El Tejon
September 2, 2004, 05:21 PM
SOT, these kids today! I blame rap music.:D

1/4, yep, you can do that. Never tried it though.:uhoh:

Rocko
September 2, 2004, 10:05 PM
Ok, so is this why some cans are advertised as 'wet capable' meaning you fill the baffles/wipes with a liquid (I've heard that a field expedient solution is urine... and what a picture THAT paints)? I'd always thought that it lowered the dB level overall but eliminating the 'first round pop' seems to make more sense.

You can add liquid/grease/etc. to pretty much any can for some additional noise reduction. The difference between those advertised as "wet" cans is that they require it to reach the advertised suppression levels and are significantly louder dry. Most modern 9mm pistol cans are "dry", while anything bigger are usually "wet" - the larger the caliber, the more difficult to suppress.

Rocko

mhdishere
September 3, 2004, 10:44 AM
Funny, I always thought a suppressed firearm (or is it "silenced"?) made a funny squeaking/zipping noise, kinda like you stepped on a mouse. At least that's what they do in the movies...

:neener: :neener: :neener: :neener: :neener: :neener:

Before you flame me, I'm joking, although I've never heard a suppressed gun before. Thanks for the video! It's nice to know there are still places you can have things like that.

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