223 vs 5.56

[Metal god]

hmm , although close the two, 40 s&w and 10mm are not the same . The cases are different because the 10mm is longer there fore causing the internal dimensions and taper of the cases are different , because of this you can not trim a 10mm case to work for the 40 S&W round . They also use different primers and IMO because of the above that makes the two cartridges very different . That is unlike the 223 and the 5.56 cases that are the same in all ways and interchangeable .

[Brian Pfleuger]

That is unlike the 223 and the 5.56 cases that are the same in all ways and interchangeable .

The CHAMBERS are not the same. THE CHAMBERS!

The brass is only part of the question.

It's all explained in the link above but I'll link it again...

http://ballistictools.com/articles/5...-and-facts.php


BTW, on the matter of 40SW and 10mm, the SAAMI spec is for external case dimension only. The differences are only about 0.001" diameter. The primer differences aren't really relevant. You could easily trim 10mm brass and WORK UP a load in .40SW. You'll note that the sizing dies are IDENTICAL and INTERCHANGEABLE. Some makers even label them .40SW/10mm Auto, just like some dies for .223Rem and 5.56. NATO. Most makers (AFAIK) don't even make a die for 5.56.

Just like .223/5.56, the problem with 40/10mm isn't the brass, it's THE CHAMBER.

[Metal god]

What does the chamber have to do with anything if the rounds them selves are loaded the exact same . Meaning , the same size case in every way , same powder charge , same primer . The only thing that's different in the head stamp and how the pressure is measured . Yes I get that the chamber will cause different pressures but the cartridge is the same ? 26gr of x powder , X- primer and X-cases only thing different is the head stamp .Therefore interchangeable .

I should add that My last couple post are as much questions as they are statement .

IMHO the real issue is ,

Is the 5.56 NATO round loaded with more powder ?
Does the 5.56 NATO round have a hotter faster burning primer ?
If measured in the same way how different would the pressures be

If the two cartridges are loaded different I understand why you should not mismatch but if they're the same ( both my books say they are ) , Why not ?

As far as the 10mm case being trimmed down for the 40 S&W . My Sierra book is quite clear that you are not to do that . Reason is the internal taper . I don't load for either so I'm basing this on what I read .

[Brian Pfleuger]

Meaning , the same size case in every way , same powder charge , same primer . The only thing that's different in the head stamp and how the pressure is measured . Yes I get that the chamber will cause different pressures but the cartridge is the same ?

If you load a .243Win, or .308 or .30-06 or any other cartridge, and you take the exact same cases, powder charges, primers and cases but you load one with the bullet jammed in the rifling and the other is not, the pressures will be dramatically different.

.223/5.56 chambers might only not be the same LENGTH, meaning the ammo built for a 5.56 chamber might jam the bullet in the lands or throat of a .223 chamber but the 5.56 chamber may also be a slightly larger diameter (see that link again). The brass will expand when fired until it contacts the chamber walls. IDENTICAL brass will NOT have identical internal dimensions if it is fired in smaller or larger chambers.

This is the same exact concept we use in handloading, why the advice is ALWAYS start low and work up. Even guns that are chambered for the EXACT same SAAMI spec chamber will not always have the EXACT same dimensions. Those minute changes can effect pressure in a DRAMATIC way.

With .223/5.56, we're not even talking about identical SAAMI spec chambers. (There is no SAAMI spec for 5.56NATO)

Look at this diagram of the chamber reamer differences. Note the differences between .223Rem and 5.56NATO, particularly the free-bore length (the single most critical difference) and the free-bore diameter. Those difference can effect pressure by many thousands of PSI.

This image shows another comparison.

Those differences might seem small but they can create major pressure effects.

[Metal god]

Sorry I was not more clear . When I said the exact same . I meant just that , including bullet , OAL etc . I get if your loading some 80gr ( not sure the correct name ) Tracer bullet into a case charged as if it was shooting a 40gr V-Max , sure big issues there . I'm trying to keep my examples and comparisons to apples to apples .

Do you know if when running the test that show mismatched chambers is bad . They were using odd NATO bullets like tracers or other bullets we will never use ? That to me would not be apples to apples .

When using my books and comparing apples to apples the 223 takes the same charge as the 5.56 and often can take .5 to 1.5gr more of powder . If you can put 1gr more of powder( with all other things being the same ) in a 223 cartridge and shoot it in a 223 Rem short throated chamber . How does that not sound conflicking to what we are lead to believe ?

Let me ask this . Does the heavy crimp and or bullet/case sealant on the NATO rounds have anything to do with pressure spikes ?

Those diagrams were cool . When looking at the first one . It would appear you can shoot 5.56 out of the 223 match chamber . The throat in the match chamber is as long as the NATO . I assume thats to allow the shooter to use 90+gr match bullets .

[Brian Pfleuger]

Sorry I was not more clear . When I said the exact same . I meant just that , including bullet , OAL etc .

I'm talking about the exact same CARTRIDGE too but the CHAMBERS are NOT the same. A cartridge that does not touch the rifling in a 5.56 might be jammed in the rifling in a .223. Note the much longer free-bore in the 5.56.

If you are a handloader and you develop your rounds using ordinary procedures, which includes knowing the length of your chamber/free-bore, there is no difference between .223 and 5.56. If you just pick up a box of ammo made for a 5.56 chamber and it's loaded long and you shoot it in a .223 chamber, you could have problems.

Does the heavy crimp and or bullet/case sealant on the NATO rounds have anything to do with pressure spikes ?

The sealant, maybe, especially in junction with a bullet jammed in the rifling because the free-bore is short. The crimp, I doubt is going to make any meaningful difference.

[Jimro]

Brian,

Generally going from 0.25" off the lands to jammed into the lands is a 7,200 psi difference with standard capacity cartridges like the 30-06.

The actual measured increase from firing 5.56 ammunition in a 223 chamber follows the same pressure increase, going from 55k to 62~63k psi.

I have yet to see a pressure test of 5.56 ammo in a 223 chamber that produced the 70k plus pressures that everyone warns about. However we have seen pressures that high due to secondary pressure spikes, and we have seen plenty of pressure traces that showed delayed ignition in 5.56 chambers (but not in 223 chambers).

I think Armalite had it right, if the ammo is malfunctioning, odds are it is an ammo problem. If reaming the chamber fixes a problem with primers sometimes popping, you still don't know if it was a chamber problem to begin with, or if you just brought opened up your chamber to be more reliable with out of spec ammo.

Then again, maybe you have a pressure trace of a mismatch that shows a huge spike in the primary pressure curve. That would be the smoking gun evidence that proves the chamber mismatch is enough to cause dangerous pressures on its own.

Jimro

[Brian Pfleuger]

I don't have any such pressure curves but the 7,200psi increase you mention is what QuickLoad expects as the increased START pressure from jamming a bullet in the rifling. The actual peak goes up a predicted 12,000 psi on a max load originally at 62,000 psi in a .223Rem default case.

If I use the slightly lower capacity 5.56 case capacity and increase the start pressure by 7,200 psi on a 62,000psi load, the peak goes to 74,800psi.

Using the SAAMI max of 55,000psi, the peak goes to 65,500psi.

[JohnKSa]

Do you have any pressure traces showing a primary pressure spike above 70k due to a chamber mismatch?

For what it's worth, one of the articles you have repeatedly quoted as a source on this thread indicates that: "...one noted gunsmith told me about a test he had heard of, conducted by an ammo manufacturer, in which 5.56 in a .223 barrel exhibited pressures of 77,000 PSI. I have no doubt that this is true..." He does caveat it by speculating that the testing was done in a test barrel.

That said, given that your explanation is essentially pure speculation and that you're trying to sell it as more likely than the one provided by at least 3 different ammunition companies (who all have access to pressure data on which to base their warnings and explanations), it would be far more reasonable for you to be the one providing data as opposed to asking for it.

The real question is: Do you have any data at all in which secondary pressure spikes were shown to have caused popped primers in ARs?

...the 223 and the 5.56 cases that are the same in all ways...

If you want to be perfectly accurate, there are small differences in the way the shoulders are formed--they are not "the same in all ways". But it is certainly true that the cases themselves are nearly identical.

As pointed out, the differences in the chambers are what is actually relevant.

[Jimro]

JohnSKa,

The real question is: Do you have any data at all in which secondary pressure spikes were shown to have caused popped primers in ARs?

Other than the presence of secondary pressure spikes using 5.56 ammo in 5.56 chambers? No.

So do you have a pressure reading showing that the mismatch produces excessive pressure in the primary pressure curve? I'd like you to respond with a "yes" or a "no" to this question at some point.

If your answer is a "no" then you should really ask yourself about how much confidence you are placing in some guy that some other guy knows who works for some company that has access to some equipment. Yes this may be a very stringent level of analysis, but when you talk about what you actually know as opposed to what you've been told, we'll have a more productive conversation.

As an engineer you wouldn't say, "well John's buddy who worked some job at ACE told me the strength of this steel was such and such, so I'm not going to do any more digging at all because that sounds like a legit way to go about my business."

Brian,

Note that the measuring technique for the 62k CIP method involves drilling through the chamber and into the brass, which is a different technique than used by SAAMI. When ammunition is loaded to 62k using SAAMI techniques it it would register WAY higher using the CIP method.

Simply put, shooting a 55k PSI SAAMI 223 Rem load through a CIP test barrel will cause it to read as 62k PSI. Same components and charge weight. The 62k figure is just a difference in measuring methodology.

But, even if you start with a full 55k PSI Nato load, adding 12k psi pressure only gets you to 67k PSI, which won't give you case head expansion or a popped primer unless the primer is not supported by the bolt face. Once again, there has to be something else going on to account for the rest of the pressure to get to 85k to expand the case head.

Jimro

[Brian Pfleuger]

Well, considering that the only difference between the two, in a general sense, is the dimensions of the throat/free-bore, I can't imagine what else that "something else" could possibly be.

I suspect that CIP's measuring system is actually more accurate. I'd say the true number is 62k, not 55k. That gets QuickLoad to 75k psi with NATO brass and the bullet jammed in the rifling.

The wild card is surplus military ammo, IMO. Something that simply doesn't exist for virtually any other cartridge combination. The neck sealant, possible bonding of the case and bullet and possibly the crimp. If each of those things added 50 or 60 pounds to the release force, you'd be looking at another 4-5,000 psi start pressure, which could push the peak to 80k or more.

[JohnKSa]

No.

The fact that you have no data that directly supports your speculative theory apparently does not give you the least pause, but at the same time you seem to think the fact that I don't personally have any pressure data somehow invalidates warnings and explanations provided by ammunition manufacturers who DO have access to pressure data on which to base their warnings and explanations.

I can see that you don't realize what an impressive double standard that is.

Once again, there has to be something else going on to account for the rest of the pressure to get to 85k to expand the case head.

Once again, it does appear that it often (though not always) requires another contributing factor that combines with the mismatch to create obvious symptoms. That has been covered a number times on this thread.

It's interesting to note that you've increased the pressure threshold to 85K, now that it's been clarified that pressures "above 70K" (your threshold from just a few posts ago) are possible due to the mismatch alone.

...how much confidence you are placing in some guy that some other guy knows who works for some company that has access to some equipment.

That's a pretty "creative" way to describe an official warning given by several ammunition manufacturers. But then it would have to be in order to avoid being merely risible.

All shooters routinely place a tremendous amount of confidence in ammunition manufacturers' dedication to safety and in their technical competence. If we didn't, we would be able to bring ourselves to put guns next to our faces and fire the ammunition that the manufacturers produce.

As an engineer you wouldn't say, "well John's buddy who worked some job at ACE told me the strength of this steel was such and such, so I'm not going to do any more digging at all because that sounds like a legit way to go about my business."

As an engineer, I wouldn't say that. And, of course, I'm NOT saying that. In fact, that's a ridiculous mischaracterization of what I've been saying.

As an engineer, I don't find it necessary to replicate testing done by other engineers who work for reputable companies simply because they didn't send me their detailed testing data to support their officially published results. Once a number of companies have paid for a particular kind of testing and if their published results all agree, the issue is settled unless there's something more weighty than speculation to call the results into question.

No engineer could ever get anything done if we all had to spend our time personally replicating or even just personally reviewing all the raw test data that's relevant to anything we're working on or interested in.

[Jimro]

Brian,

The difference between a SAAMI and NATO chamber as far as I can determine from the technical drawings is 0.002 inches to the start of rifling, then the major difference is the angle of rifling, the SAAMI distance is 0.095" until full rifling, the NATO chamber is 0.116" until full rifling. There is a number 0.164" which doesn't have an arrow pointing to a dimension in the NATO drawing that I don't know what to do with.

Obviously the NATO chamber gives a longer reduced rifling friction interface, but the surfaces involved are 0.004" at maximum interference, with a distance difference of 0.021".

But once again, if we look at the CIP measuring methods for 223 Rem, we note that the spec for 223 Rem (not NATO) starts at 62k PSI, so if we make the logical leap that the only difference between the 5.56 NATO spec of 58k and the 223 Rem spec of 62k PSI (a logical leap the Europeans made that I'm following), we have a 4K psi increase that we can lay at the leade of the chamber. This falls in line with the data reported by luckygunner.

But, once again, even if we start at 62k, add, 12k to say that the bullet is jammed into the lands, we are still not at case head expansion pressures (still 11k psi shy of case head expansion).

So the "other considerations" really do go back to the ammo. Soft brass, bad powder, oversized bullet, secondary pressure spike, long neck pinching the bullet, etc.

That and M193 was never NATO standard, so all those imported M193 rounds advertised as 5.56 should be meeting the American milspec 55k max pressure (measured by mid case method) have a dubious pedigree at best. Even the Israeli imports for Winchester white box have had bad lots known to pop primers. There was a whole thread on which lots to avoid for Q3131a over at arfdotcom.

The reason why I keep bringing up secondary pressure spikes is that they are most severe with light projectiles and a ball powder on the slow side. That the milspec powder charges for M193 lists 28 grains of WC844 inclines me to believe that lot to lot variance could be one of those "other factors" that pushes up pressure, even after the bullet has left the bore if deflagration rapidly turns to detonation. We more often see M193 loads pop primers than M855 loads, and the only real difference is the 10% projectile mass difference.

The pressures are spec'd the same, the powder used is the same, WC844, but the projectile mass is more in line with the burn rate. The bad lot of Radway Green SS109 used "British 4895" powder, but based on the reports of folks using that lot, soft brass is the more likely culprit (many reports of failure to fire even with strong primer hits, likely as the cases deformed absorbing impact energy) plus the popped primers that indicate a pressure problem even in 5.56 chambers.

Jimro

[Jimro]

JohnSka,

85k was the pressure noted by Clark in his tests. And we started talking about the different measuring methods used between SAAMI and CIP, so please let me apologies for not being more clear about that. I guess for clarity's sake I should label PSI with "CIP" or "SAAMI" the way we used to add "CUP" when that measurement was confused with the piezoelectric measurements.

The working max pressure for the Mk248 Mod1 round was spec'd by NSWC for 68k PSI. Different case of course, but shows no signs of case head expansion, which means if you had to do a proof load based on that, you are pushing 90k.

I've been trying to think of an analogy that will explain to you why I am the way I am.

And as an engineer you only trust reliable sources.

Is your doctor a reliable source? Most people would say yes, they have years of highly technical training to hone their craft.

Twice since I graduated from college I've had interactions with Board Certified M.D.'s who failed to understand what I would consider basic pharmacology. One had me explain to him the purpose of the Henderson-Hasselbach equation and why ionization states at a given pH were important for drug delivery. The other was a Pediatrician who prescribed antibiotics to my wife while she was pregnant when the listed contraindications for that medication included pregnancy.

That combined with my training in chemistry is to "make the math add up" to stand on its own.

For a more real world example, everyone knows spinach is a good source of iron right? Wrong, the iron content of spinach was magnified by a decimal error which was then published and accepted as true because it came from a reliable source.

When a beam fails, you suspect that there was a problem in the manufacture of the beam, not that your respected source of information was incorrect about the load bearing strength of a wide flanged beam. When ammunition fails, I see an ammunition problem first.

When I see what is described as an overpressure event, I want to figure out first if it was an overpressure event, second, what was the proximate cause of the symptoms, and lastly determine if it is repeatable. I've seen cases ripped apart on the first firing from DOD accepted ammunition lots. It happens, you can't know how every round in a lot will perform without testing every round, which defeats the purpose of manufacturing ammunition for use by Soldiers in the first place. So we do a statistical sampling that gives us good warm and fuzzies that we used enough to pick up a bad lot. It doesn't always work that way.

So that is why I have focused so much on pressure trace data, because it is actual data. Not something that everybody knows, not something you heard or read, but something that is actually describing what is going on. Making the math add up.

Jimro

[JohnKSa]

Twice since I graduated from college I've had interactions with Board Certified M.D.'s who failed to understand what I would consider basic pharmacology.

I have had similar experiences--far more than only two, and with other "reliable sources" than just doctors. As a result, I always look for second opinions, and feel much better when I can get more. And I never feel bad about doing a little additional research on my own.

In this case, the bases are more than covered. We don't have to rely on the opinion of a single expert. Not even just two, three, four or five experts.

We have, instead, a statement from a company, a statement representing the consensus of multiple experts. And in case we still feel like that's unsteady ground, we have the same statement from another company. And from a third. On top of that, we can add the opinions of multiple independent experts in the field of concern.

So that is why I have focused so much on pressure trace data, because it is actual data.

No, that is not what you have focused on. What you have focused on is trying to pursue the red herring of whether or not I, personally, have pressure trace data.

You know, and I know, and everyone, who has even a sketchy idea of what this thread is about, knows that the ammunition companies who have issued the warnings definitely have access to pressure trace data on which to base their warnings.

That is why I queried you, early in this discussion, as to whether you were claiming that the ammunition companies and experts don't know what they're talking about, or whether you were claiming that they are engaged in some sort of conspiracy to mislead the shooting public. Because that's what this is really about.

In order for you to make any reasonable progress in terms of supporting your claim that you have a better explanation than the ammunition companies and experts, you'll need to either prove that they don't know what they are talking about or that they are conspiring to mislead us.

Trying to make a point of the fact that I don't have pressure trace data is not even the first step down the road of achieving the burden of proof that you will need to satisfy.

[Brian Pfleuger]

Originally Posted by Jimro

The difference between a SAAMI and NATO chamber as far as I can determine from the technical drawings is 0.002 inches to the start of rifling, then the major difference is the angle of rifling, the SAAMI distance is 0.095" until full rifling, the NATO chamber is 0.116" until full rifling. There is a number 0.164" which doesn't have an arrow pointing to a dimension in the NATO drawing that I don't know what to do with.

From this diagram, it looks to me that the start of the rifling is 0.033 farther out with NATO.

The diameter directly in from on the case mouth is 0.226 in NATO, where it's 0.224 in Rem. That 0.002 may allow some gases to escape and lower pressure before the bullet seals the bore.

In that drawing, the full rifling begins at (0.073+0.164) 0.237 in NATO and at (0.040+0.045) 0.085 in the Rem. That's difference of 0.152. The reamer drawing indicates a free-bore difference of 0.0316 and a throat angle more than twice as sharp in the Rem.

One of the problems possibly being that there is no US standard for what constitutes "5.56". Ironically, I also see no CIP standard for 5.56. They list cartridges and diagrams on their site. They show only .223Rem.

In any case, I'm convinced that those chamber differences and possibly coupled with problems associated with surplus military ammo are the source of the problem. For a handloader, the cartridges are identical. For the guy with a .223Rem and a handful of military surplus 5.56, they are most certainly not.

[Jimro]

JohnSKa,

No, that is not what you have focused on. What you have focused on is trying to pursue the red herring of whether or not I, personally, have pressure trace data.

You know, and I know, and everyone, who has even a sketchy idea of what this thread is about, knows that the ammunition companies who have issued the warnings definitely have access to pressure trace data on which to base their warnings.

That is why I queried you, early in this discussion, as to whether you were claiming that the ammunition companies and experts don't know what they're talking about, or whether you were claiming that they are engaged in some sort of conspiracy to mislead the shooting public. Because that's what this is really about.

Knowledge falls into realms of things we believe to be true, and things we've proven to be true. It isn't a red herring for me to ask you to prove your statement, but you simply can't.

You have to believe it to be true because you haven't proven it to be true. As an engineer that is not a problem. Engineers don't care whether an electron is a particle or a wave or how it transitions between those states, simply that it works in a circuit.

Reminds me of what a mathmatician told me some time ago when we were discussing modeling problems. "Working in calculus the class was split almost even between math majors and engineering majors, the instructor would assign problems for home work with the caveat 'engineers solve it, mathematicians prove it.'"

Simply looking at the data and saying, "well, I had these problems, and reaming the chamber solved the issue I was having" doesn't mean you proved what was going on, something YOU HAVE ALREADY AGREED TO WHEN YOU LISTED ALL THE OTHER POSSIBILITIES THAT PRODUCE POPPED PRIMERS.

But once again, you can't show me that the chamber mismatch produces that spike in the primary curve to a level that would pop a primer, because we don't have a chamber pressure curve trace that shows that. If we did, you would have pointed it out by now. So the math doesn't add up, and the chamber mismatch explanation doesn't work until you add in an ammunition problem.

You can claim that I'm spouting a conspiracy theory or red herrings, but really all you are doing is resorting to an ad hominem attack to draw attention away from the fact that you can't PROVE what you BELIEVE to be true.

If you CAN prove what you BELIEVE to be true, I'm all ears.

Jimro

[JohnKSa]

It isn't a red herring for me to ask you to prove your statement, but you simply can't.

How did this get to be "my statement"? What you've asked me is if I have pressure data that proves what the ammunition companies and other independent experts claim is true.

Then, because I do not, you seem to think that the fact that I don't have the raw data somehow calls the statements of the ammunition companies and experts into question. Any thought at all will demonstrate how completely ridiculous that is. How could my having or not having raw pressure trace data possibly affect the validity of the ammunition companies' claims? Clearly it can't.

If we did, you would have pointed it out by now. So the math doesn't add up, and the chamber mismatch explanation doesn't work until you add in an ammunition problem.

Again, this is ludicrous.

The fact that I don't have the raw pressure trace data absolutely does NOT mean "the math doesn't add up". It just means I don't have the raw data. IF we had the raw data we could look at it and decide if the math added up or not, but NOT having it doesn't prove anything other than that we don't have the raw data.

What you're saying is the equivalent of claiming that because Frank Jones (some random guy on the internet) can't come up with raw particle accelerator/collider data showing the existence of the Higgs Boson, that therefore the math doesn't add up and so now we can safely conclude that the Higgs Boson particle doesn't exist.

Of course, in reality, the fact that Frank Jones doesn't have personal access to the raw data has absolutely no bearing whatsoever on the existence of the Higgs Boson particle and a person who attempted to claim otherwise would be proving nothing other than that they had some really serious shortcomings in terms of logical reasoning ability.

If you want to disprove the claims of the ammunition companies and experts, you need to prove that THEY do not have access to, or are misrepresenting pressure data. Proving that "Frank Jones" doesn't have it doesn't buy you anything at all.

[Brian Pfleuger]

I find it almost beyond belief that this is even a question.

The standard creed of Handloaders is "Start Low and Work Up!"

Why?

Because bad things can happen if you start at max load. NO ONE seriously disputes that. UncleNick has reported knowledge of starting loads being too hot in some guns.

How could that be?

Because all chambers, barrels and components are not identical and so unforeseen things happen.

This, when the chambers of the firearms in question are SUPPOSED to be IDENTICAL, with the only variance being in manufacturing tolerance.

Now, we have the case of the .223Rem and 5.56NATO that are SUPPOSED to be DIFFERENT and we've got people telling us , "Ah hell! They're the same damn thing! Load 'em up!"

It's asinine beyond belief.

[Jimro]

JohnSKa,

Epistemology deals with how we deal with knowledge, how we discern truth.

Right now, you believe that you have the truth because you trust the sources you've trusted. There is nothing particularly dangerous about your beliefs, but you can't prove them, which is why you have continually attacked my position with such words as "ludicrous, red herring, ridiculous, and 'confirmation bias'"

But you ignore the quote "this can happen in any rifle and any caliber!" from the link I referenced and instead focused on "this should not happen in a tight bore barrel 20" or less." to accuse me of not reading my own source data.

That you are getting angry or frustrated means that somehow I'm challenging you to actually think in a way that is uncomfortable for you, possibly because you don't like questioning authority, especially the authority that you trust to give you reliable knowledge. Somehow I'm getting a response from you that is similar to someone spouting heresy in a religious setting.

The fact stands that we have no primary source of data showing the mechanism of a chamber mismatch bringing pressure levels to where we would see popped primers. I can't find one, you can't produce one, and believe me it would end this conversation right quick if it was out there and available.

If you twist the theory to fit the data, you are more likely to come to the correct conclusion than twisting the data to fit the theory. I don't have the data to prove the conventional wisdom true, so I base my understanding on the actual evidence available (hearsay is not evidence).

To sum up my understanding, a chamber mismatch will result in a modest and predictable chamber pressure increase, but it will not produce an overpressure even unless there is an associated ammunition defect.

But if we start quoting experts instead of data, then we are simply falling prey to the "argument from authority" fallacy which doesn't do anyone any good.

Jimro

[JohnKSa]

Right now, you believe that you have the truth because you trust the sources you've trusted.

You have completely missed the point. While it is true that I (as anyone should) have more confidence in the warnings provided by multiple ammunition companies and idependent experts than I have in theories provided by anonymous folks on the internet, that is really a secondary issue.

The primary issue has more to do with addressing your objections to the warning/explanations to the sources, and especially the shaky "logic" you have used to defend those objections and the theory you have proposed.

That you are getting angry or frustrated means that somehow I'm challenging you to actually think in a way that is uncomfortable for you...

I'm not angry, and to the extent that I'm frustrated it is not because you have challenged me to think differently. It is because you:

1. Don't seem to see how logically bankrupt some of your reasoning is.
2. Repeately raise the same issue over and over again even after it has been definitively addressed. (more on that later in this post)

...I base my understanding on the actual evidence available (hearsay is not evidence).

This is, of course, not true since you have already admitted that you have no "actual evidence" to show that secondary pressure spikes have caused popped primers in ARs. You have theorized that they might, and have gone so far as to say that it's a more likely explanation than the one provided by the ammunition companies and experts, but you have, admittedly, done so in the absence of any "actual evidence" showing that any AR has ever popped a primer as the result of a secondary pressure spike.

I don't have the data to prove the conventional wisdom true...

Which means ONLY that you, personally, can not personally prove that the explanation provided IS true. It does not, in any way, give you the abilty to prove that the explanation is NOT true.

The inability to prove a premise is NOT equivalent to the ability to disprove that premise. The fact that I have no way to personally prove the existence of the Higgs Boson does NOT automatically mean I have disproved, or can disprove, its existence.

Furthermore, your lack of direct access to this data does not, in any way, call into question the warning/explanations provided by the ammunition companies and experts. Just like Frank Jones' lack of direct access to raw particle accelerator/collider data doesn't in any way call into question the explanation of the physicists who do have access the data and provided their conclusions.

But if we start quoting experts instead of data...

The idea that we can't accept anything as valid without looking at the data ourselves is ludicrous. As I mentioned earlier, if we get information from multiple, independent reliable and authoritative sources who all agree, it is reasonable to assume, in the absence of hard evidence to the contrary that the information is reliable.

If everyone had to prove everything for themselves, if everyone had to examine the raw data for themselves, the field of human endeavor would have stalled long ago when it became impossible for one person to be able to understand all of science and technology sufficiently to prove/examine everything personally before relying on it.

...we are simply falling prey to the "argument from authority" fallacy which doesn't do anyone any good.

Getting back to the second source of frustration mentioned above, there are at least two more examples from this latest post. This quote is one.

On page 2 of this thread, you made a similar comment about the "argument from authority" fallacy and I pointed out that your understanding of the fallacy is incorrect and provided some links and quotes that explained the correct meaning of the argument from authority fallacy.

That basic pattern has been a theme on this thread. You raise an issue and it is definitively addressed and yet you go on as if that never happened, raising the same issue again, sometimes only a few posts later, as if it were a new objection.

...focused on "this should not happen in a tight bore barrel 20" or less." to accuse me of not reading my own source data.

Here's another example. As I have already pointed out, at least twice previously, the quote is that "SEVERE" secondary pressure spikes should not occur in barrels 20" or less. Yet, in spite of that, you have raised the same objection again as if I had not already addressed it accurately.

[Jimro]

JohnSKa,

1, You can't show a pressure trace showing anything more than a normal, repeatable expected rise in the primary pressure curve from a mismatch.

2, I can show data showing secondary pressure spikes late in the firing cycle with 5.56 chambers, and a severe secondary pressure spike in a worn match AR.

Your objections to the secondary pressure spike data is that in the 5.56 data from lucky gunner it wasn't high enough, and that in the shootingsoftware.com it was with a match rifle. My response is that if the pressure coincides with extraction that even normal pressure can pop a primer out (in fact a partially popped primer in a bolt action rifle is associated with a low pressure event) and that the source noted that "this can happen in any rifle in any caliber" and hedged their language noting that "severe secondary pressure spikes shouldn't happen in a 20 inch or less tight bore barrel." So a less than severe pressure spike at the right time in the extraction cycle could give you a popped primer when the bolt face is not supporting the primer.

This explanation fits the facts and data available, without any missing pressure.

The alternate "common wisdom" explanation is that the extra friction of the leade spikes pressures to over 85k psi which expands the case head and causes the primer to go flying out on extraction. But we don't have any actual recordings of this happening, and only data showing a repeatable, not dramatic increase in pressure.

That still leaves us with math not adding up, where is the pressure coming from that is popping primers? The only actual data source we've seen that could do that is the secondary pressure spike reported with Winchester 55 grain ammunition.

And that is my "shaky" logic.

Now here is the kicker, I can't "prove a negative" which means that I can't prove that there won't be an event somewhere at some time that isn't solely due to a mismatch.

Jimro

[JohnKSa]

1, You can't show a pressure trace showing anything more than a normal, repeatable expected rise in the primary pressure curve from a mismatch.

1. Irrelevant. Since the warnings do not originate from me, the fact that I do not have access to the pressure trace data in question means nothing. If you can prove that the ammunition companies have made the warning in the absence of any pressure data to support the warning, THAT would be relevant.

2. This objection has already been raised and answered multiple times on this thread.

2, I can show data showing secondary pressure spikes late in the firing cycle with 5.56 chambers, and a severe secondary pressure spike in a worn match AR.

1. Given that the pressure spikes are under SAAMI max in all cases involving barrels of 20" or less, it is a mischaracterization to call them severe.

2. Given that the pressure spikes did not result in popped primers or any other signs of overpressure events in barrels of 20" or less, it is a mischaracterization to call them severe.

3. This claim has already been made and answered multiple times on this thread.

My response is that if the pressure coincides with extraction that even normal pressure can pop a primer out (in fact a partially popped primer in a bolt action rifle is associated with a low pressure event) and that the source noted that "this can happen in any rifle in any caliber" and hedged their language noting that "severe secondary pressure spikes shouldn't happen in a 20 inch or less tight bore barrel." So a less than severe pressure spike at the right time in the extraction cycle could give you a popped primer when the bolt face is not supporting the primer.

1. Your theory seems plausible. It may well be that the secondary pressure spikes DO sometimes result in popped primers in ARs in spite of the fact that you have presented no data to demonstrate that it actually has or does.

2. If you ARE eventually able to document that secondary pressure spikes can cause popped primers in ARs, that will not disprove the ammo/chamber mismatch warning since the ammo/chamber mismatch warning does not claim that an ammo/chamber mismatch is the only possible source for popped primers or other overpressure events.

3. This point has already been raised and addressed multiple times on this thread.

That still leaves us with math not adding up, where is the pressure coming from that is popping primers?

1. It does not leave us with the math not adding up since there is nothing in the warning that precludes other contributing factors from increasing the pressure. Chamber temperature, high ambient temperatures, etc. can all raise discharge pressures. When you combine a number of factors which don't commonly result in severe overpressure, the combination of those factors are known to and can be demonstrated in some cases to sum and result in a pressure that is higher than the single contribution of any one of the factors in isolation. Combine that with multiple sources indicating that the mismatch alone can cause pressures in excess of 75K and you have a more than adequate and completely credible explanation for how the ammo/chamber mismatch can cause popped primers in a situation where they would not otherwise occur.

2. This objection has already been raised and answered multiple times on this thread.

(I'm not trying to be objectionable by pointing this out, but at some point, isn't enough enough? How many times do we need to cover the same ground before we decide the grass on it is really and truly trampled to death? It would be one thing if you could raise a new point or rebut the counterpoint; simply reposting a point that has already been put to rest doesn't benefit anyone at all.)

...I can't prove that there won't be an event somewhere at some time that isn't solely due to a mismatch.

On a practical note:

Because we don't shoot our firearms in tightly controlled laboratory conditions where we can insure that there are no additional contributors which might raise pressures, there's no real-world benefit of being able to demonstrate that the ammo/chamber mismatch can't be the "sole" cause of an overpressure event.

The entire point of such warnings is that because it's not possible to control all the circumstances rigorously, it becomes more critical to control the things that can be controlled. The knowledge that the damage/injury from an overpressure event was due to multiple contributors and not just a single one would not be any consolation at all.

[Jimro]

Brian,

I'd like to remind you of the Armalite warning.

The first few rounds of ALL ammunition, from whatever source or lot, should be checked for signs of pressure or any other defect before firing large quantities. If you have a problem, you can generally bet that the ammunition meets neither SAAMI nor NATO specifications.

When there isn't a mismatch folks generally blame bad ammo. When there is a mismatch, folks generally blame the mismatch. It doesn't matter what chamber leade you have if the ammunition is bad.

To address JohnSKa's concern,

It does not leave us with the math not adding up since there is nothing in the warning that precludes other contributing factors from increasing the pressure. Chamber temperature, high ambient temperatures, etc. can all raise discharge pressures. When you combine a number of factors which don't commonly result in severe overpressure, the combination of those factors are known to and can be demonstrated in some cases to sum and result in a pressure that is higher than the single contribution of any one of the factors in isolation. Combine that with multiple sources indicating that the mismatch alone can cause pressures in excess of 75K and you have a more than adequate and completely credible explanation for how the ammo/chamber mismatch can cause popped primers in a situation where they would not otherwise occur.

Having a complete credible explanation is not the same thing as having actual data to prove the complete credible explanation. You say this is irrelevant. Let it be known that the NATO proof load for 5.56 is 77,958 PSI (537.5 MPa), and the proof load, intentionally overloaded, does not pop primers.

However since NATO specification calls for ammo to be tested at high temperatures to simulate a desert deployment, blaming temperature as a proximate cause for a chamber pressure spike is pointing to ammunition that would have failed NATO specification testing. You can check the NATO EPVAT testing criteria for yourself, suffice to say that it is rigorous.

Let me quote a DTIC report:

Within NATO small caliber ammunition standardization, the NATO Design Mark has no official significance. It is generally accepted that the ammunition with this mark should, but cannot be guaranteed, to chamber correctly in a weapon. It should not be assumed though, that it will produce the expected performance or necessary level of safety required by the STANAG and MOPI.

This is the reason why the Brits I met in Iraq told me that they could not use American Lake City M855 ammunition through their L85 rifles, but that we could use their SS109 ammunition made by Radway Green. Both are NATO weapons, both loads are "NATO Spec" but true interoperability was not achieved.

Jimro

[JohnKSa]

Let it be known that the NATO proof load for 5.56 is 77,958 PSI (537.5 MPa), and the proof load, intentionally overloaded, does not pop primers.

My last post (as well as several others I have made on this thread) already addresses this. Even if we are willing to accept that a proof load doesn't pop primers in ARs **, that assumption doesn't preclude the ammo/chamber mismatch from being the primary contributor in popped primers and other overpressure events since "we don't shoot our firearms in tightly controlled laboratory conditions where we can insure that there are no additional contributors which might raise pressures".

"Combine that with multiple sources indicating that the mismatch alone can cause pressures in excess of 75K and you have a more than adequate and completely credible explanation for how the ammo/chamber mismatch can cause popped primers in a situation where they would not otherwise occur."

**It is probably worth pointing out the source for this factoid that you have repeatedly stated as truth.

Originally Posted by Jimro

Unfortunately 77k psi won't pop the primers out. Case head expansion doesn't start until 85k psi according to Clark, who has tested more cartridges to failure than I care to count (and I believe him on this), and primers don't pop out until pressures are higher than that.

Originally Posted by Jimro

85k was the pressure noted by Clark in his tests.

No offense meant to Clark, but for research purposes, he is essentially an anonymous source. You have repeatedly taken me to task for citing the consensus of conclusions of multiple ammunition companies and other independent experts, making statements like: "Right now, you believe that you have the truth because you trust the sources you've trusted." and accusing me of "quoting experts instead of data".

I've tried to use other points to demonstrate that you are operating with a pretty impressive double-standard and are apparently not aware of it, perhaps this will resonate a little more strongly.

It appears that one of the major pillars of your theory is based on a quote from an anyonymous source. Using your own standards, you should not have relied on this quote unless you were in possession of the pressure trace data that the source used to demonstrate that 223/5.56 primers will not pop at 77Kpsi.

At the very least, using reasonable research standards, you should not have relied on it in the absence of corroborating evidence from authoritative and reputable sources.