Suppressors Barrel length and suppressors

[Shooter McGavin]

I have a Tac Ops 5.56 suppressor that I had mounted on an Aero Precision 10.5” SBR. I never check what the decibel level was on it. However, I did try and shoot it without ear pro and I’m sure I did permanent damage.

I saw a YouTube vid saying that 11.5” barrel increases the FPS by 100 fps over a 10.5” barrel. So I figure it burned more of the powder off. That said I purchased a BCM 11.5 upper for my SBR and put the Tac Ops 5.56 can on it. While using ear pro I shot the weapon and checked the decibels. It averaged 109 decibels with Federal 55gr plinking ammo. So, I removed my ear pro and shot it and it wasn’t bad at all. I will still shoot it with ear pro, but I was pleasantly surprised and now will use this SBR a lot more.

 

[Huskydriver]

109 DB is low guaranteed. How we're you measuring the DB?

Glad you learned shooting unsuppressed hurts your ears before you went deaf.

 

[hafejd30]

Ya I don’t think your readings are correct. The bolt alone is at least that. And your in the teens generally speaking with 300 blackout subsonics suppressed. Anything supersonic is going to be around at least 140. Are these subsonic 55 gr?

 

[AIAW]

Wish I had a picture of my buddies that he ran on a 10.5" for years. Essentially ate the first baffle completely out of it. Impressive to say the least. Repaired, no worries!

 

[Shooter McGavin]

Ya I don’t think your readings are correct. The bolt alone is at least that. And your in the teens generally speaking with 300 blackout subsonics suppressed. Anything supersonic is going to be around at least 140. Are these subsonic 55 gr?

This is just the standard Fed 55 grain. I measure at the muzzle (end of the suppressor).

 

[hafejd30]

Ya I think you need another decibel meter. Most suppressed AR 15 will be around 140 ish at the bolt (at least on a DI gun) and around low to mid 130’s where your measuring from. I don’t think you understand how quiet 109 decibels is. I’ve run a Thunderbeast ulra 9 for several years on 16” AR’s. There regarded as one of the quietest suppressors on the market. And I’ll guarantee you I’m lucky if I’m below 130 decibels at the muzzle with that. Not saying it can’t be real, but I think the results are lying to you.
Clap your hands once. That’s probably closer to 109

 

[hafejd30]

I’m just guessing that the supersonic crack of the bullet is over 109 even. I know standing in the pits at fclass matches we still wear ear pro and if you don’t have it you’ll feel the difference. Sounds like a 22 rifle going off in a field. But I really don’t know how loud the supersonic crack is decibel wise

 

[mikesmith13807]

This is just the standard Fed 55 grain. I measure at the muzzle (end of the suppressor).

What are you measuring with?

 

[mikesmith13807]

I’m just guessing that the supersonic crack of the bullet is over 109 even. I know standing in the pits at fclass matches we still wear ear pro and if you don’t have it you’ll feel the difference. Sounds like a 22 rifle going off in a field. But I really don’t know how loud the supersonic crack is decibel wise

OSS did a video with MAC about this. The bullet flight was still around 130 db even when the shooter was hundreds of yards away. I think they said the line of flight was maybe 25 yards from the meter.

 

[Shooter McGavin]

The more I google this, it doesn’t seem possible. I used this app with my race car for when I have to add baffles to my car to make noise levels and it’s been right on with their test equipment. That said it just doesn’t seem possible to get these results. I will say it’s a lot quieter on the 11.5 vs the 10.5.

 

[mikesmith13807]

The more I google this, it doesn’t seem possible. I used this app with my race car for when I have to add baffles to my car to make noise levels and it’s been right on with their test equipment. That said it just doesn’t seem possible to get these results. I will say it’s a lot quieter on the 11.5 vs the 10.5.

Yeah those apps have some use for constant sound but only very expensive equipment can accurately measure the fast rise time and short impulse peak of a gun shot. Meters that are decades old still cost thousands of dollars.

Go look through the spreadsheet at nfatalk.org to get an idea of typical levels--they use good equipment.

 

[Shooter McGavin]

Yeah those apps have some use for constant sound but only very expensive equipment can accurately measure the fast rise time and short impulse peak of a gun shot. Meters that are decades old still cost thousands of dollars.

Go look through the spreadsheet at nfatalk.org to get an idea of typical levels--they use good equipment.

Thanks

 

[Darkside-Six]

I don’t know, but I’ve been running a 10.5 for years on my MK18 and run it hard and haven’t had any issues.

 

[Zak Smith]

109 is not credible. You need a 2209 at minimum to accurately measure rifle fire.

 

[Huskydriver]

109 is not credible. You need a 2209 at minimum to accurately measure rifle fire.

You mean my play store app for my Android doesn't give me valid DB readings?!!!

 

[missilemantdi]

Yeah, what Zach said...There are basically two sound meters that meet the req's for suppressor sound measurement until you step up to piezo pressure transducers and a fancy data acquisition system. And the android or iphone do not meet these req's to say the least. I heard one person state that they measured 79dB out of a suppressor, while my real meter said that a dryfire of the same rifle measured 110db. And as another example, a suppressor on a bolt gun reads 125db and the same suppressor reads 145db on an AR gas gun.

The meter shown in the OSS video isn't technically mil-spec unless the revision was approved recently and I haven't seen it.

 

[mikesmith13807]

The meter shown in the OSS video isn't technically mil-spec unless the revision was approved recently and I haven't seen it.

I think that's MAC's meter they were using--I once asked OSS customer service what they used and was told they use the Pulse system.

From what I understand MAC's meter doesn't technically meet the milstd requirements but it appears to generate useful data--his numbers aren't much different than what I've seen from various 2209s.

 

[Almonz]

Your readings seem way off. 5.56 is still technically not hearing safe with a can. Even out of a 16" barrel mine tickles the ear drums.

 

[BuildItYourSelf]

The reason a 11.5" will send a bullet faster over a 10.5" is simply because there is 1 more inch of travel the bullet is pushed. The powder is completely burnt in the first few inches in a proper cartridge set up. Obviously there are cases unburnt powder is sent out of the barrel. Mostly caused when a slow burning powder doesn't reach enough pressure to properly accelerate the burn. Most cases tho it's completely burnt before two case leangths.
The fire ball is mostly extra carbon and hydrocarbons reacting with oxygen because it's at a high enough temperature to convert.
Powders have to have extra or "free" carbon to prevent oxidation in the bore.
Sound levels drop with barrel length simply because pressure and heat lower with leangth as well.
A suppressor works by slowing the rate of pressure release and soaking up heat. So the less pressure and heat it has to deal with the better it will be able to do so.

In addition. There are different loads one can use to better accommodate a subsonic pistol leangth suppressed rifle. The goal is to have a clean burn with just enough pressure to achieve desired speeds. In the case of 223 its not as easy as say 300blk. Small case volume and heavy projectiles make the task less difficult.

 

[Tuukka]

Bullet flight noise is c. 150 dB for .223/.308 measured 1 m from the bullet flight path.

On a SBR type AR platform rifle you will be at c. 138 - 142 dB at the shooters left/right ear. ( unsuppressed level c. 158 - 160 dB )

Best Regards!

Tuukka Jokinen
Sales director, MIL/LE

Ase Utra sound suppressors