Does A Longer Barrel Reduce Noise Of Fired Shot?

[arakboss]

I've often heard that AR pistols produce more noise than AR rifles. Has anybody accurately measured this? Assuming you were firing the same type of ammo from each barrel, does a longer barrel reduce noise from fired shots? If so how much noise reduction percentage wise per inch of additional barrel length. Also if it's true, does it apply to smooth bore barrels as well?


Edit: How could you use different powders to achieve similiar velocities but reduce noise?

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[bcp]

A couple of studies:

Quote from:

Barrel Length Studies in 5.56mm NATO Weapons – Small Arms Defense Journal

sadefensejournal.com

"Simple usage of these short-barreled weapons has shown the necessity for both sound and flash suppression, the intensity of which (in exceptionally short barrel lengths) approached the intensity of a flash-bang diversion device."

===========================

Another study

https://digitalcommons.usf.edu/cgi/viewcontent.cgi?article=1014&context=honors_et

Bruce

 

[The B]

yes.

from personal experience firing a 20" m16a2 with no ears on, which is totally tolerable (surely still terrible for your ears, especially if repeatedly), to firing a 10.3" mk18cqb with no ears on... was like getting punched jn the face. stunned me for a couple seconds till i remembered i didnt have ears on

 

[The Heretic]

The longer the barrel, the more time and space that the hot gases have to expand and slow down.

That is all a suppressor does; provide volume for gases to expand and use baffles to slow the speed of the gases.

So the answer to your question is yes.

Supersonic projectiles will still produce a shockwave though.

 

[Cerberus Group]

Got a friend with a bolt action rifle chambered for 300 BO that has a 26" barrel. With shooting subsonic rounds, it's dead quiet...no suppressor.

 

[trevi]

A couple of studies:

Quote from:

Barrel Length Studies in 5.56mm NATO Weapons – Small Arms Defense Journal

sadefensejournal.com

"Simple usage of these short-barreled weapons has shown the necessity for both sound and flash suppression, the intensity of which (in exceptionally short barrel lengths) approached the intensity of a flash-bang diversion device."

===========================

Another study

https://digitalcommons.usf.edu/cgi/viewcontent.cgi?article=1014&context=honors_et

Bruce

So, in essence, shooting blanks in an AR pistol could count as flash bangs?

 

[Dans_Militaria]

Got a friend with a bolt action rifle chambered for 300 BO that has a 26" barrel. With shooting subsonic rounds, it's dead quiet...no suppressor.

Now that… sounds like something I need to try

 

[trevi]

A couple of studies:

Quote from:

Barrel Length Studies in 5.56mm NATO Weapons – Small Arms Defense Journal

sadefensejournal.com

"Simple usage of these short-barreled weapons has shown the necessity for both sound and flash suppression, the intensity of which (in exceptionally short barrel lengths) approached the intensity of a flash-bang diversion device."

===========================

Another study

https://digitalcommons.usf.edu/cgi/viewcontent.cgi?article=1014&context=honors_et

Bruce

So, in essence, shooting blanks in an AR pistol could count as flash bangs?

I've often heard that AR pistols produce more noise than AR rifles. Has anybody accurately measured this? Assuming you were firing the same type of ammo from each barrel, does a longer barrel reduce noise from fired shots? If so how much noise reduction percentage wise per inch of additional barrel length. Also if it's true, does it apply to smooth bore barrels as well?


Edit: How could you use different powders to achieve similiar velocities but reduce noise?

Ever been to an outdoor range, shooting next to someone shooting an AR pistol. LOUD! You can almost feel the shockwave.

 

[Yarome]

...does a longer barrel reduce noise from fired shots?

Absolutely, but at some point it comes at a trade-off. Too long in the barrel and you can experience negative drag that will impact velocity. I don't know what the decibel impact would be per inch of barrel, but I would think it would be very firearm and ammo specific. Taking into account not just being the barrel length, but potentially also the mechanical elements (ie., buffer and spring, gas system in an AR, etc) that would also directly impact pressures and barrel dwell time to a degree. Toss in a muzzle device and "felt" sound mitigation can be tremendous.

 

[RX-79G]

Absolutely, but at some point it comes at a trade-off. Too long in the barrel and you can experience negative drag that will impact velocity.

If you get to that point, gas pressures would be very low. Sounds like a formula for making a quiet gun - barrel length longer than peak velocity.

 

[Member 3687]

comparison between 10.5 and 16 in and with a suppresser
About 1db average

 

[Yarome]

If you get to that point, gas pressures would be very low. Sounds like a formula for making a quiet gun - barrel length longer than peak velocity.

Yup. Of course, you could just adjust your load to accomplish the same in a shorter barrel.

 

[Member 3687]

When I was shopping for silencers I watched a lot of vids showing short and long barrel ARs unsilenced then silenced and 1 to 2db max seemed to be the average difference between 10.5 and 16 inch unsilenced.

They say 3db is a noticeable sound difference to the average ear. I feel the big difference is the barrel muzzle is closer to your face and so it is louder in your mind and you can also feel the concussion more but that is just my opinion.

 

[aksu747]

Got a friend with a bolt action rifle chambered for 300 BO that has a 26" barrel. With shooting subsonic rounds, it's dead quiet...no suppressor.

I believe it, I was at the range a few years back with my uncle and he was shooting .38 special through a long barrelled lever gun and it was ridiculously quiet.

 

[Will_White]

Yeah just think of a 22 pistol vs a 22 rifle, the pistol makes your ears ring and the rifle can be shot comfortably (NOT hearing safe).

There's also a company that sells 32" barrel extensions for shotguns that work like a supressor.

 

[The Heretic]

So, in essence, shooting blanks in an AR pistol could count as flash bangs?

Ever been to an outdoor range, shooting next to someone shooting an AR pistol. LOUD! You can almost feel the shockwave.

I stood next to a .50 M2 while it was shooting. I felt it. I also felt some dynamite go off about 40' in front of me.

 

[dangerranger60]

I have a single shot 22 rifle with a 30" barrel that when shooting sub sonic ammo is quieter than any of my pellet guns. the same ammo from an 18" barrel sounds like a 22 rifle. DR

 

[arakboss]

I am eager to get my cheapo 24" 223 Wylde non threaded bull barrel up and running to compare noise levels against some shorter barrels.

 

[Alexx1401]

So, in essence, shooting blanks in an AR pistol could count as flash bangs?

Ever been to an outdoor range, shooting next to someone shooting an AR pistol. LOUD! You can almost feel the shockwave.

The first time I had someone in the lane next to me indoor with an AR pistol I thought he was shooting one of the hand cannons. I had double protection on and it was amazing. When I saw the .223 brass on the floor I was shocked it was so damn loud.

 

[dangerranger60]

I am eager to get my cheapo 24" 223 Wylde non threaded bull barrel up and running to compare noise levels against some shorter barrels.

Try finding someone with a 7" pistol barrel and compare with the same ammo. DR