SBR Noise

[alamo5000]

DELETED

[Slippers]

You're certifiably insane. :)

[Joelski]

Internal/transitional ballistics involves physics, black magic and gypsy tears. Far geekier than external and terminal...

It's all about the bang and the hole.

[alamo5000]

You're certifiably insane. :)

I do try!

Where would the 'Evolution' part of the evolution come from without a little bit of insanity?

Seriously though...To get similar velocity, reduce pressure, reduce back pressure, and still have an accurate 100 yard load? Why not try? I have a $50 gift card waiting to be spent to find out...

I have no way of knowing if the reduced pressure will make the suppressor more efficient or not though. I can only assume it will to some degree.

[alamo5000]

Internal/transitional ballistics involves physics, black magic and gypsy tears. Far geekier than external and terminal...

It's all about the bang and the hole.

Do you seriously know who you are talking to here???

I am el-king-o of the geek squad... ask anyone

I am the prince of impossibly dumb questions and mad science.

[alamo5000]

You guys seriously make fun of me now, but one day I will invent something cool like the CD player or VCR and you won't be laughing then!

I will have the biggest gun collection ever!

[Jerry R]

Just to toss in my two cents on the original question -

how much louder a short barrel is than say a 16" gun and really a basic explanation of 'why' this is so.

...

I cannot tell you "how much louder" - that would require a DB Meter, but I can give you my understanding of "why"

The 'noise' is the burning rate of the gunpowder - basically it burns and expands faster than the speed of sound. I think I read somewhere that most burn rates are in the neighborhood of 40,000 FPS plus/minus based upon individual powder's burn rate - please do not hold me to that, I can't find it again. That being said, the longer the barrel, the more powder burns (and expands [pressure]) inside the barrel. A shorter barrel may allow powder to burn after exiting the barrel - or at least continue its' expansion outside the barrel - depending upon the powder burn rate and amount of powder used. Barrel length should therefore determine how much expansion is contained - noise level. That large fireball coming from a short(er) barrel may or may not be unburned powder, but it is representative of the continuing expansion (noise) and pressure relief. Suppressors work (I believe) on the basic premise of slowing and cooling the expanding gasses with baffles; i.e., the pressure/fireball/expansion is contained.

Final comment - I may be full of crap, but I can make almost anything sound logical.

If someone has a better or more accurate explanation, please share it. Again - this is just my understanding of the process; and I may be completely off base.

[GRIFFIN ARMAMENT]

16" Ar15's have an SPL of ~164DB, the 10.5's 168 so you are looking at about 4DB difference before accounting for the muzzle devices influence on that. Granted, a muzzle brake could push a 16" to 170 or higher at 90 degree/1M, so that plays a part in it. I'm talking about A2 compensator readings as a baseline, A-weighted (which is about 8DB more quiet than unweighted)< weighting is a frequency curve for reporting of data- it is designed to replicate human auditory frequency ranges, but some have argued that C weighting makes more sense, and OSHA's scale is a C scale. C is closer to A than unweighted.

Shortening the barrel causes the moment of "uncorking" the bullet leaving the barrel, to happen at a higher peak pressure, and pressure release creates noise. 14.5" pressure is something like 8KSI, 10.5 is 11.5KSI and 7" is ~17KSI.

Brakes compress, localize, and redirect blast pressure, increasing sound at 90 degrees and at the shooters position dramatically- 7-14DB.

The Recce 5 has a pressure driven baffle system, and generally performs better with increased pressure- so resultant SPL is = or lower in most cases. That's a general rule that at least seems to be reasonably accurate from 10.5-16" At ear noise is going to be more a function of barrel length (distance of muzzle pressure from shooter) and gas system length (proximity and peak pressure of gas system venting into the action) of course, so at ear noise on a pistol gas 7.5" barrel is louder than carbine gas 10.5 for example.

At a point there is an inverse relationship- I would expect a 7.5" barrel to be louder than a 10.5 with probably 60% greater volume of gas- with all suppressors shortening barrel length at a point overwhelms the suppressor system and begins to bleed over into sound performance loss. This is probably because the volume of gas is greater for shorter barrels- because unburned powder is discharged into an oxygen rich environment and burns inside the can, defeating the purpose of the silencer which is to allow gas to expand and diminish in pressure. That is countered by virtue of gas expanding via the secondary mechanism of continued powder ignition inside the suppressor system. The bullet inside the barrel creates a high pressure, working gas somewhat inside the barrel and allowing powder to near completely burn at lengths of about 18" which is ideal for the suppressor in that it introduces "dead" hot gas that is done expanding and is ready to begin pressure reduction.

Not needlessly abusing a suppressor is a good thought process. 3 mags puts the can at about 900F, which is about the threshold where abusive use begins. The cans can be run to probably 1500F or maybe a little higher, but at those higher temperatures any metal on earth is getting softer and wear is accelerated, and also the metal is in an environment in which it is being metallurgicaly changed and losing strength with exposure time.

[DeviantLogic]

I feel smarter after reading Griffin's post. Great explanation.

[DeviantLogic]

One day I will invent something cool like the CD player or VCR

Dude, those already exist...

[Txfilmmaker]

Dude, those already exist...

No way! Really?


Sent from my iPhone using Tapatalk

[Joelski]

16" Ar15's have an SPL of ~164DB, the 10.5's 168 so you are looking at about 8DB difference. Granted, a muzzle brake could push a 16" to 170 or higher at 90 degree/1M, so that plays a part in it. I'm talking about A2 compensator readings as a baseline, A-weighted (which is about 8DB more quiet than unweighted)< weighting is a frequency curve for reporting of data- it is designed to replicate human auditory frequency ranges, but some have argued that C weighting makes more sense, and OSHA's scale is a C scale. C is closer to A than unweighted.

Shortening the barrel causes the moment of "uncorking" the bullet leaving the barrel, to happen at a higher peak pressure, and pressure release creates noise. 14.5" pressure is something like 8KSI, 10.5 is 11.5KSI and 7" is ~17KSI.

Brakes compress, localize, and redirect blast pressure, increasing sound at 90 degrees and at the shooters position dramatically- 7-14DB.

The Recce 5 has a pressure driven baffle system, and generally performs better with increased pressure- so resultant SPL is = or lower in most cases. That's a general rule that at least seems to be reasonably accurate from 10.5-16" At ear noise is going to be more a function of barrel length (distance of muzzle pressure from shooter) and gas system length (proximity and peak pressure of gas system venting into the action) of course, so at ear noise on a pistol gas 7.5" barrel is louder than carbine gas 10.5 for example.

At a point there is an inverse relationship- I would expect a 7.5" barrel to be louder than a 10.5 with probably 60% greater volume of gas- with all suppressors shortening barrel length at a point overwhelms the suppressor system and begins to bleed over into sound performance loss. This is probably because the volume of gas is greater for shorter barrels- because unburned powder is discharged into an oxygen rich environment and burns inside the can, defeating the purpose of the silencer which is to allow gas to expand and diminish in pressure. That is countered by virtue of gas expanding via the secondary mechanism of continued powder ignition inside the suppressor system. The bullet inside the barrel creates a high pressure, working gas somewhat inside the barrel and allowing powder to near completely burn at lengths of about 18" which is ideal for the suppressor in that it introduces "dead" hot gas that is done expanding and is ready to begin pressure reduction.

Not needlessly abusing a suppressor is a good thought process. 3 mags puts the can at about 900F, which is about the threshold where abusive use begins. The cans can be run to probably 1500F or maybe a little higher, but at those higher temperatures any metal on earth is getting softer and wear is accelerated, and also the metal is in an environment in which it is being metallurgicaly changed and losing strength with exposure time.

At what temp does the heat treat start to suffer? What I'm learning from this thread is that while I wouldn't intentionally abuse my suppressor, I also don't want to leave a pristine can behind when I die. I plan to use it and enjoy it for what it is and not stress over wear and tear. The part of your post about gasses combusting under expansion makes a case for an inert gas injection system to be the next big thing in weapon suppression! SCIENCE!!!

[alamo5000]

First off.... THANK YOU for the absolutely stellar answer. AAAAANNDD Griffin hit's a homerun with that one!!!!

Now down to more business...

Shortening the barrel causes the moment of "uncorking" the bullet leaving the barrel, to happen at a higher peak pressure, and pressure release creates noise. 14.5" pressure is something like 8KSI, 10.5 is 11.5KSI and 7" is ~17KSI.

So in my original hypothesis of creating ammo that from the get go has lower original chamber pressure, wouldn't that allow 'decorking' to occur at much lower PSI and thus (maybe) mitigate some of the PSI blast and allow for slightly better suppression?



Max PSI there in that load is 39.000 vs the measured 55.000+ with M855 in those previous tests. I am just saying in theory if this were possible to accomplish would the (relative) lower PSI aid in suppression in anyway? It would have a benefit of less back pressure for sure. It could also over time if you in theory shot nothing but those lower PSI rounds help not put the can under 'as much stress'...but the real question is if you metered a 10.5 gun with a Recce 5 vs an 18" gun with a Recce 5 the longer gun have better inherent suppression (as you said because of max efficiency of the nature of the gas), but would the relatively lower PSI round be worth trying to test out? At least in theory it would put the two guns about in the same ball park with of course some variances. But I am talking specifically about ammo and the dynamics it plays....

Of course I do acknowlege that with the 18" gun you are talking about maximum efficiency of the can because of the nature of the gases....

If you could decork a 10.5 at 7500 PSI instead of 11,000 PSI would that provide any kind of benefit? Audibly or otherwise?

Is it worth it to try? What do you think about the nature of the experiment I have in mind? Under $50 and hey it's a possibility to do... and in theory I wouldn't be using max loads... but 55.000 vs 39,000 is a substantial difference....

Brakes compress, localize, and redirect blast pressure, increasing sound at 90 degrees and at the shooters position dramatically- 7-14DB.

That's a general rule that at least seems to be reasonably accurate from 10.5-16" At ear noise is going to be more a function of barrel length (distance of muzzle pressure from shooter) and gas system length (proximity and peak pressure of gas system venting into the action) of course, so at ear noise on a pistol gas 7.5" barrel is louder than carbine gas 10.5 for example.

This actually makes sense... the physical proximity to the muzzle is much closer to the ear with a short gun... all else being equal 6" directly closer, combined with a particular muzzle device that redirects the sound outwards...it can 'seem like' the gun is louder and depending on how that noise is directed it just may be....

But that does bring up an obvious benefit of the muzzle blast director that I just bought. In theory that answers that. The sound waves naturally want to travel in a radial motion, IE a firecracker suspended in space going off... the sound will go equally in all directions, or want to for the most part, but if it's on the ground the blast becomes more like a 'dome' because the sound bounces off the earth... but with a blast shield those waves are directed forward to be more mushroom shaped out and away from the shooter and it can lessen it to the sides as well.

Of course I will be testing the thing when it arrives, but that makes a lot of sense. It sold it for me, even though I already bought one before I knew that. :)

Not needlessly abusing a suppressor is a good thought process. 3 mags puts the can at about 900F, which is about the threshold where abusive use begins. The cans can be run to probably 1500F or maybe a little higher, but at those higher temperatures any metal on earth is getting softer and wear is accelerated, and also the metal is in an environment in which it is being metallurgicaly changed and losing strength with exposure time.

Yes, this is what I understood as well through my research on the subject... not to say you can't go enjoy the can... of course...that is 100% the reason why I bought it in the first place, but if you're a change the oil every 3000 miles kind of guy like I am it's just a rough guide to not abuse my investment....

[alamo5000]

I feel smarter after reading Griffin's post. Great explanation.

Yes sir! Absolutely. I wasn't expecting such a great and knowledgeable answer. That is just awesome.

The more you know... the better off you are.

[GRIFFIN ARMAMENT]

At what temp does the heat treat start to suffer? What I'm learning from this thread is that while I wouldn't intentionally abuse my suppressor, I also don't want to leave a pristine can behind when I die. I plan to use it and enjoy it for what it is and not stress over wear and tear. The part of your post about gasses combusting under expansion makes a case for an inert gas injection system to be the next big thing in weapon suppression! SCIENCE!!!

About 1100F and above. ~3.5-4 30 round magazines dumped on full auto will reach that on a 10.5" barrel, and the can will cool at a rate of about 240F per minute from a peak of 1100F (first minute only- after which subsequent minutes from lower temp will have lower rate of change).. The finish we currently use holds to 950F so 3 -30's is its threshold. The cans are incredibly strong and the material will only degrade to a point it is about as strong as inconel 625 (in a worst case hours and hours of soaking at 1500F), but for best results using the can under 1000F (in normal use) and then saving brute force abusive episodes for those apocalyptic SHTF senarios that probably exist more in fantasy than reality, would be a strategy to provide the greatest life expectancy of the product. When the can is hotter, the material is temporarily more subject to errosive wear, so the higher temperature of operation, the worse wear will be. When the can hasn't been soaked at high temperature to the point of significant reduction of strength, the brute force ability of the can to survive an unbelievably abusive event is very high. For example, Sage dynamics ran 500 rounds of 5.56mm through a 10.5" barrel and M4SDK in 4 minutes 50 seconds. No damage except for the paint finish 90% removed.

The 17-4 we use exclusively in most of the centerfire suppressors is the tube material for the blast chamber on the Rugged Surge 7.62 which they shoot on belt feds until it is glowing in daylight and have said is "Belt fed rated"

So really the question you are asking is a philisophical one, "What is your opinion of an intelligent way to use the product." Because they obviously run the can with total disregard for the metalurgical change that is occurring and their marketing materials give them impression it is of no consequence. My response is conservative and based on my interpretation of hundreds of pages of data I've read on 17-4 stainless steel.