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alamo5000
29 December 2015, 19:38
Prepare yourself for another one of my nerd alert threads [:D]

I have test fired my 10.5 pistol aka soon to be SBR and the thing is basically loud.

I am wondering if anyone knows just how much louder a short barrel is than say a 16" gun and really a basic explanation of 'why' this is so. Basically none if this is trouble shooting or 'need to know' but rather I am try to expand the knowledge base and maybe understand more principles of sound as it relates to guns.

Maybe the Griffin guys will swing by and add their 3 cents.

Why does shortening the barrel add noise? Why does everyone complain about 'that guy'... the one with the brake? Technically wouldn't a compensator be just as loud as a brake? Or is the bitching because the blast is directed out to the side more with a brake?

I am running one of these on my short gun:

http://cdn3.volusion.com/zwlmq.eyhrp/v/vspfiles/photos/GATMHC556-2T.jpg?1446204959

So as a baseline I am talking straight up gun noise.

Next I am adding in the use of a suppressor (in my case a Recce 5)...and how much suppression occurs when starting from a higher baseline of noise such as a 10.5 barrel?

I wonder what the actual metering would be on a 10.5 barrel with a Recce 5... vs on a longer barrel? Does the silencer become less efficient with a shorter barrel or is it because the baseline for noise is just that much more? Hopefully that makes sense.

Another thing is someone gave me an ebay gift card for Christmas and really I didn't want anything from ebay...so I shopped around and found one of these:

http://cdn3.volusion.com/zwlmq.eyhrp/v/vspfiles/photos/GATMBS-2T.jpg

My thought process for buying that is, yes I will run my silencer on both guns (obviously) but sometimes I might want to run the short gun without one. For those times when I really want to run the gun harder I can use the blast shield... I don't want to damage my suppressor from doing mag dump after mag dump... 3 mags in of running hard and you're pretty much over the heat limit (per a youtube video--which they actually measured the temp of a suppressor from start to finish when running hard)...

I am thinking that little blast shield might 1) look pretty cool on the muzzle, but also 2) direct the concussion out and away from the shooter's position. It will still be loud but it may or may not add something that wasn't there before.

Long story short thanks to the gift card I got a brand new blast shield for almost nothing so I am not really out anything.

But if I am out and we have 3 or 4 people and they all want to shoot the (eventual) SBR I don't want to run my silencer that hard. In those situations we can put up with the overall noise but I wouldn't want to run my suppressor that hard to where it's baking off the finish or damaging the can. Plus without the can on I can take advantage of the shorter OAL of the gun.

Really there are 3 or 4 questions or topics in there so maybe we can get some amateur and hopefully some expert input here.

alamo5000
29 December 2015, 19:45
Here is a youtube video that GA made about those blast shields...


https://www.youtube.com/watch?v=k7wM_7kAv6g

alamo5000
29 December 2015, 19:59
Also I would like to throw in another question that is pretty technical in nature... if you watch this video at 20:00 in they do the whole heat test on a suppressor...


https://www.youtube.com/watch?v=2HzMLvrF6u4


My other question is it seems like a very short barrel (like a 10.5) will generate a lot more heat in a shorter amount of time for a suppressor.

Is that true and can it be quantified in any kind of relevant numbers?

To me the shorter the barrel the closer you are to the blast and hence more heat...

So the question is about suppressor use on a short barrel... specifically as it relates to heat.

They did that test above in the video... I think it would be cool to do a similar test using a 10.5 and see if there is any heat generation difference based on barrel length...

Former11B
29 December 2015, 20:06
Did you eat paint chips as a kid? [BD]

alamo5000
29 December 2015, 20:09
Did you eat paint chips as a kid? [BD]

Dirt. Lots of dirt. LOL!!!

My questions really are brilliant ya'll just haven't realized it yet [BD] HAHAAHAAA!!

SwissyJim
29 December 2015, 20:18
Did you eat paint chips as a kid? [BD]
LEAD paint chips! [:D]

I think a lot of it is the powder is still burning while it exits the barrel, hence the more flash/bang. Of course powder selection for reloading can come into play here. Also look at the suppressors info- there are limits to barrel length they are warrantied to.

I was looking at having my Saiga12 turned into a short barrel, and Tony Rumore @ Tromix told me to wear gloves with anything 10" and shorter...

alamo5000
29 December 2015, 20:30
LEAD paint chips! [:D]

I think a lot of it is the powder is still burning while it exits the barrel, hence the more flash/bang. Of course powder selection for reloading can come into play here. Also look at the suppressors info- there are limits to barrel length they are warrantied to.

I was looking at having my Saiga12 turned into a short barrel, and Tony Rumore @ Tromix told me to wear gloves with anything 10" and shorter...

I had frosted lead chips with milk every day for breakfast for my entire 4th grade year [BD]

As to powder I have wondered about this too...how powder selection can be different for shorter barrels. Something faster burning might be good. I have some so I might experiment, but I am no Molon. Anything I do would be anecdotal.

I did hear that most powder is already burned within the first so many inches of the barrel but since fluid dynamics isn't really my gig I don't know. Too scientific even for me, but if anyone knows by all means...

My silencer is warrantied down to 7.5" so it has no problem handling a 10.5 barrel... I was really kind of asking that part so I can maintain my suppressor or at least try to. (You have to see the 2nd video to know what I am referring to...)

SwissyJim
29 December 2015, 20:43
mmm...frosted lead chips! LOL

I saw a post somewhere, regarding pistol loads, but it showed the difference in muzzle flash between two powders with (supposedly) close burn rates. I'll see if I can find it again. I do know that certain powders make a differnce. Like I have all but given up on 5744 in my 30BLK as I always have a LOT of unburned powder granules in the barrel with it.

alamo5000
29 December 2015, 20:52
mmm...frosted lead chips! LOL

I saw a post somewhere, regarding pistol loads, but it showed the difference in muzzle flash between two powders with (supposedly) close burn rates. I'll see if I can find it again. I do know that certain powders make a differnce. Like I have all but given up on 5744 in my 30BLK as I always have a LOT of unburned powder granules in the barrel with it.

I have a 1 pound bottle of IMR 4895 but I am normally shooting Varget.

On this chart the IMR is #89 on the list and Varget is #99.

http://www.lasc.us/BurnRatePrint.htm

It might not make one hill of beans worth of difference but then again when you get down to shooting pistol length barrels I don't know why it wouldn't make a difference.

alamo5000
29 December 2015, 22:09
http://sadefensejournal.com/wp/wp-content/uploads/2012/02/barrel5.jpg


Maybe I stumbled upon a semi answer to one of my questions... Check the chart above...Look at the PSI @ muzzle exit. The shorter the barrel the greater the PSI, which it turn would mean the suppressor would have to deal with this increased pressure.

alamo5000
29 December 2015, 22:20
"In recent years, designers have become aware of limitations to suppressor structural integrity due to rapid pressure variations in the entrance chamber of their suppressors. The entrance chamber is easily visualized as a simple cylinder that acts like a pressure vessel with a hole in the far end to control the rate of pressure decrease. With gunfire, the pressure peaks almost instantaneously and drops literally in microseconds. A lot of structural stresses are applied in this short time interval. A firearm barrel can also be visualized as a pressure vessel, but one of varying length as the bullet progresses throughout its length."

http://www.sadefensejournal.com/wp/?p=1093

alamo5000
29 December 2015, 22:36
So in theory if you were wanting to make a 'maximum' cartridge for suppression for an SBR... you would need to select a powder based around PSI in the chamber, not always velocity. So in theory if you could come up with or choose a powder that has less pressure then you are onto something as to getting better suppression out of a shorter barrel.

At first glance Winchester 748 with a 55 grain bullet has a pressure between 39200 psi and 48500 psi... With a 55 grain bullet that will get you still in the ballpark on velocity.

IMR 4064 would be another good choice for less pressure....That is 37,100 psi to 44800 psi... you would still be right around the velocity mark as well...

That is assuming you want to load for better suppression...and not self defense or whatever.

alamo5000
29 December 2015, 22:46
A 55 grain soft point with Winchester 748 powder shows a MAX load of 26.3 grains and a MAX pressure of 39,000....

That is WELL below what others are at.

Varget for example which is kind of middle of the road with the same bullet has a max pressure of 49,700 almost 10,000 more PSI difference with velocity difference of only around 200 fps....

So basically you could still easily end up at the 2600 fps velocity threshold out of a 10.5" barrel with either... only the one has a lot less pressure... which should make it a lot more quiet to shoot. (with a suppressor)

https://c2.staticflickr.com/2/1574/23436435944_876d90f8d5_b.jpg

alamo5000
29 December 2015, 23:18
In the tests above (linked below as well) their chamber pressure was measured at 55,744 psi....with m855 ammo.

http://www.dtic.mil/ndia/2010armament/WednesdayCumberlandPhilipDater.pdf

If you subtract 11,500 for the 10.5" exit pressure you have a difference of 44,244...divide by 10.5 and that's 4213 psi per inch of barrel that it goes down. Or in percentage terms 20% of the chamber pressure was the muzzle exit pressure.

With my theoretical ammo above using the max loads and max pressure using winchester 748 powder and a 55 gr SP bullet... the max pressure in the chamber is 39,000 psi... times that by 20% and you have an estimated 7800 psi exit pressure... which should make it about as quiet as the same suppressor on an 16" barrel using m855 ammo....and out of a 10.5 barrel you will still be up around that 2600 fps velocity...

I think it's worth an experiment...the point being trying to make my suppressor more efficient on a short barrel...and seeing if it will work like that...that's my hypothesis...

alamo5000
30 December 2015, 06:21
https://c2.staticflickr.com/2/1625/23956348232_72b146898c_b.jpg


https://c2.staticflickr.com/2/1647/23768818330_63a2d61ba7_b.jpg

alamo5000
30 December 2015, 06:31
DELETED

Slippers
30 December 2015, 07:18
You're certifiably insane. :)

Joelski
30 December 2015, 07:20
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
30 December 2015, 07:26
You're certifiably insane. :)

I do try! [:D][:D][:D]

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

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
30 December 2015, 07:29
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???[BD][BD][BD]

I am el-king-o of the geek squad... ask anyone [:D]

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

alamo5000
30 December 2015, 07:33
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! [:D]

Jerry R
30 December 2015, 09:14
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. [BD]

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
30 December 2015, 10:34
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
30 December 2015, 10:42
I feel smarter after reading Griffin's post. Great explanation.

DeviantLogic
30 December 2015, 10:44
One day I will invent something cool like the CD player or VCR

Dude, those already exist...

Txfilmmaker
30 December 2015, 11:29
Dude, those already exist...

No way! Really? [emoji41]


Sent from my iPhone using Tapatalk

Joelski
30 December 2015, 14:46
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
30 December 2015, 18:25
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?

https://c2.staticflickr.com/2/1574/23436435944_876d90f8d5_b.jpg

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
30 December 2015, 18:36
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
2 January 2016, 11:18
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.

GRIFFIN ARMAMENT
2 January 2016, 11:39
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?



YES absolutely you would reduce the sound of the firearm both with and without the suppressor. This would be similar to 300BLK. It produces a somewhat sedate unsuppressed numbers for SPL.

Re decrease in pressure and value of pursuing it:

YES of course- a decrease in pressure will cause a decrease in sound. You will probably also lose velocity with the pressure decrease though. That's probably why people don't pursue it.

Re comment on oil:

Yes I change the oil on vehicles every 3000 miles. Despite the fact that the transmission usually ends the vehicle and the engine would probably run on 150K more miles. So I'm probably actually wasting some money and 3000 probably isn't the perfect number, given other major components will end the life of the vehicle ahead of time.

Joelski
2 January 2016, 14:39
Ditch the dino stuff. I put synthetic in the tranny, diffs and transfer case too. Crankcase lube gets changed yearly and still looks good.

alamo5000
23 January 2016, 19:58
OK so I did a little bit of experimentation... I bought a pound of Winchester 748 because that one has the lowest listed CUP value out of all the powders on Hogdon's reloading data.

According to Hogdon's data a 55gr SPR SP has a CUP value of 39,000 at max load...

Well I didn't use Speer Soft point bullets... I bought a box of 1000 Hornaday FMJ 55gr and tested with that.

The only other bullet that they have listed at 55gr that compares the powders is a Barnes TSX FB... with that bullet the CUP values are much closer...48,500 vs 50,300 at their max loads...

https://c2.staticflickr.com/2/1551/23945124313_a530234bb6_b.jpg

Long story short I loaded rounds to almost identical (pretty close) velocity averages and there was marginal, if any, difference in sound. Of course I don't have a meter but there was no discernible difference in sound.

Anyway I almost satisfied my curiosity about the Winchester powder...It actually works great for plinking ammo and it meters really well. I just basically finished off the pound of powder so I have a couple hundred loaded 55 grain rounds now.

On a side note the powder was somewhat cheaper than some of the others and as I said it meters really well so later on up the road I might get some more to make plinking rounds with.

alamo5000
23 January 2016, 20:28
I am getting way over my head here but I am reading about CUP vs PSI and those two are NOT the same thing. At best they have a rough correlation to each other. From what I can tell CUP values are estimates only whereas now they are actually measuring PSI in some cases.

CUP generally measures peak pressure...so basically my theory is that the properties of the powder do make a huge difference in CUP and in PSI. So say you had a powder that had a violent expansion...the CUP would be pretty high...but if you had a powder that had more of a controlled burn the CUP might be really low. That said the actual PSI to get the bullet down range is obviously still present although how it gets there is slightly different. Google and read up on how they measure CUP if you are curious about it. It will make more sense...

I learned something but this is getting too nerdy even for me... [:D]

Long story short myth busted.

Also don't use CUP and PSI interchangeably like I was thinking... they are not the same thing.

Former11B
23 January 2016, 20:38
Did you learn that 160 dB sounds the same no matter which powder you use. [BD]

alamo5000
23 January 2016, 20:38
Also if you notice on the data on their reloading page that I pulled... one is listed in PSI (the Barnes) and the other is listed in CUP (the Speer)...

I didn't notice that until just now. The measurements for the Barnes now seem like they are more accurate across the board because it is two entirely different measurement systems.

alamo5000
23 January 2016, 20:40
Did you learn that 160 dB sounds the same no matter which powder you use. [BD]

I learned that they way they measure pressure is entirely different. I was comparing apples to oranges... [BD]

CUP does not equal PSI [:D]

alamo5000
23 January 2016, 21:45
Basically from what I gather the measurements for CUP have been around quite a while... they have a test barrel with a small piston attached to the chamber. On the other end of that piston they place a carefully calibrated piece of copper (or lead for some rounds). When the gun goes off it forces the piston up and it crushes the copper. From that they determine CUP pressure estimates.

PSI on the other hand is just what it sounds like... PSI...

So basically as I said before... if your powder has a quick 'flash bang' component to the design of it the CUP will be more... but if the powder is designed to be more of a controlled expansion then obviously it won't send that piston up to crush that piece of copper nearly as hard...hence 'less peak pressure'...but by the time that bullet reaches the end of the barrel though there still is substantial PSI.

At the end of the day though PSI is what matters. Under pressure then the decork=the boom.