quote:

Originally posted by SmokinJ:

It's illegal for a firearms or ammunition manufacturer to use a strain gauge for developing their products and the real is simple.....they aren't nearly accurate enough.

back to this.. there are several misstatements in your post..
1: it is NOT illegal, by any sense of the word - you've been asked to present the law in this matter, and can't. you then stipulated some conclusion regarding nato/un taking over shipping. you were widely incorrect, on several points. sorry, can't take your word for it
2: you lump fire arms manf into this.. which has nothing on earth to do with ammo pressure and testing authorities ... it might SEEM reasonable to lump them together, from someone with ZERO experience with actual pressure testing, and to someone of equal experience. however, not even "winchester" makes winchester ammo and winchester guns.

3: "it is real simple" is YOUR opinion.. and no basis in fact. its apparent you have nil first hand experience with them... or even 3rd hand experience with someone that knew what they are doing with one. scientific fact, within their range of error, their results are very repeatable and verifiable... they are, in fact, at least as good as high end chronographs....

4: inconclusion, i think you might have shot off your fingers, without thinking you'd be called on it. we aren't gunstore browsers, waiting to be impressed by the counterstop ninja's here.. sorry, but your suposition is dead wrong, and its up to YOU to prove the illegality of said practice.

oh, yeah, i've owned and used these things.. and its shocking how close quickload compares in pressure and spikes

Clem:

As to your question regarding formulae to calculate pressure.

The answer is yes there are a number of formulae, most are historical.

The problem is that they are not simple to use and each one has limitations and built in error because of how various factors that effect pressure is weigted or in some cases ommitted in the formula.

Possibly the most commonly known formula used in the USA is that of Le Duc and it's application in the form of the Powley slide ruler.

Le Duc and Powley slide rule assumes a number of limits such as a load density of 85% and barrel resistance is omitted, ie it assumes a frictionless gun system.

Le Duc's formula or method actually was used by not only the US Defence establishment but also by all of the major publishers of sport shooting load data until around the 1970's. So by design there is a built in overestimation of say velocity and a underestimation of pressure.

One of the major problems facing the use of any formula is the fact that a randomness exists in the internal ballistics event.

Furthermore there is a direct correlation in the magnitude of the randomness based on caliber.

So that in large caliber guns such as Naval Guns, mortars and cannons the range of intershot randomness in say pressure data is relatively small and the formula deviates little from actual shooting data but as the caliber gets smaller the spread of actual data gets bigger, and the formula data deviates by larger amounts from the actual data.

So that if we look at say small caliber shoulder fired weapons in say the 22 caliber range the spread of intershot data for pressure can be as high as 5000 or 6000 psi and this is for a single gun using same load and components !

Add to this then the roughly 5% of variation attributable to difference between individual guns and components and the magnitude of variation becomes very large.

quote:

Originally posted by Clem:
... is there a formula for calculating ... pressure? ...

Yes, but is way to complex to go into here.

quote:

Originally posted by jeffeosso:

quote:

Originally posted by SmokinJ:

It's illegal for a firearms or ammunition manufacturer to use a strain gauge for developing their products and the real is simple.....they aren't nearly accurate enough.

back to this.. there are several misstatements in your post..
1: it is NOT illegal, by any sense of the word - you've been asked to present the law in this matter, and can't. you then stipulated some conclusion regarding nato/un taking over shipping. you were widely incorrect, on several points. sorry, can't take your word for it
2: you lump fire arms manf into this.. which has nothing on earth to do with ammo pressure and testing authorities ... it might SEEM reasonable to lump them together, from someone with ZERO experience with actual pressure testing, and to someone of equal experience. however, not even "winchester" makes winchester ammo and winchester guns.

3: "it is real simple" is YOUR opinion.. and no basis in fact. its apparent you have nil first hand experience with them... or even 3rd hand experience with someone that knew what they are doing with one. scientific fact, within their range of error, their results are very repeatable and verifiable... they are, in fact, at least as good as high end chronographs....

4: inconclusion, i think you might have shot off your fingers, without thinking you'd be called on it. we aren't gunstore browsers, waiting to be impressed by the counterstop ninja's here.. sorry, but your suposition is dead wrong, and its up to YOU to prove the illegality of said practice.

oh, yeah, i've owned and used these things.. and its shocking how close quickload compares in pressure and spikes

Okay Jeff, in a nut shell we both are right and wrong.

It's very hard to give you a link about the legalities of the strain gauge. As Larry Gibson said all major industries use them...but that is it...none of them actually state they publish reloading data from them. Instead what they do is use the strain gauge to check their other method. In short because "absolute chamber pressure is what is wanted" a strain gauge can't give you that, they are advised by their legal team not to use the strain gauge solely for publishing reloading data. A strain gauge also needs a verified pressure to calibrate it. One thing a strain gauge can do that the others cannot is "duh" tell you the stress or strain of the metal that it is attached to. The other methods cannot tell you that. Two very knowledgeable men in this field have an on going argument over chamber pressure. The says what is important is what the brass (the case) can take and let go at.

Not pertaining to our little argument, Hotcore is very correct about the formulas for all the pressure measurements being so huge that they would about fill this whole thread.

SmokinJ

Joe, you really need to quit while you're behind because you keep digging the hole deeper.

In short because "absolute chamber pressure is what is wanted" a strain gauge can't give you that,

Excuse me? The CUP method only gives that and it is called "peak pressure". A strain gauge and transducer with give not only the peak pressure but the time/pressure curve of each shot. That is something CUP can not do.

they are advised by their legal team not to use the strain gauge solely for publishing reloading data.

To quote from the movie; "who is they"? The ammunition industry is quite large so could you be specific by naming the companies and how you got that information? I ask because I know of several that use the M83 Oehler in testing and developing their product and their data.

A strain gauge also needs a verified pressure to calibrate it.

Joe, you really must do a little more research as your lack of knowledge here is getting embarrassing. Strain gauges are "calibrated" at manufacture. With each gauge you get the "calibration data" that is inputted into the program. The copper crushers of the CUP system also must be "calibrated". You get a tarage table with them and without that you can not measure the crush and determine the pressure. Piezo transducers also must be calibrated (quite often actually) before use. Additionally "reference” ammunition is used to verify velocity and psi readings. A discrepancy between what the reference ammunition is supposed to have and what the test fixture records is called an "off set". That off set is then added or subtracted from the test fixtures readings to give the supposed psi and velocity. This is because all test fixtures are different, same as all guns are different - even in the same cartridge.

One thing a strain gauge can do that the others cannot is "duh" tell you the stress or strain of the metal that it is attached to. The other methods cannot tell you that.

You finally got something that is correct. What the relevance is escapes me however.

Two very knowledgeable men in this field have an on going argument over chamber pressure. The says what is important is what the brass (the case) can take and let go at.

No real argument there; the fact is that modern brass cases can contain pressure before showing any measurable expansion to a much higher degree than is safe for many actions. Secondly many times the cases do not expand until the psi gets into a gross over pressure or proof load situation. I recently tested some Winchester .223 M193 ammunition. The average peak psi was 65,700 psi. There was also an attendant 200+ fps gain in velocity. Obviously that is a bit of an over load yet there was no measurable case head expansion. That kind of "fact" is all too prevalent when using CHE. CHE is no longer an acceptable method of pressure measurement because it is unreliable. BTW; if using CHE how does one "calibrate" the lot of cases used to know what any measurable expansion means in psi?

Lastly I would ask you or anyone; where in the world, locked away in some government vault, is a standard one pound per square inch? What is the standard? Well, there isn't any. One psi is calculated or measured by testing the effect of pressure on something.

All psi measurements, CUP, transducers, strain gauges and questimations such as "Quickload" are all computations. The differences are “equivalencies" as such. None are "absolute" and all very to a degree. What Remington gets with .308W "reference" ammunition in their test barrel is going to be different from what Winchester gets, what Federal gets and what you and I get in our commercial barrels. That is why ammunition companies and now most loading manuals give data that follows SAAMI guidelines concerning MPLM (MAPs), MPSMs, and MEVs in load development. The use of Peizo transducers and strain gauges now allow that because they give a much better and complete picture of the time/pressure curve where as the older CUP method does not. Most factory ammunition is loaded below the SAAMI MAP (MPLM) for that cartridge contrary to most everyone's belief that they are all loaded to max psi. For example, the MAP (Maximum Average Pressure) for the .308W is 62,000 psi. I have yet to find a factory round that hits that average psi.

So Joe, I suggest you do a lot more research or get some hands on experience with a properly set up strain gauge machine to measure firearm psi such as an Oehler m43 or M83. If you do that then you might have some knowledge of what you speak. Now you don't and continue to post erroneous information and assumptions. You know what happens when you "assume" because that's what you're making yourself look like.

Larry Gibson

quote:

Originally posted by Larry Gibson:
SmokinJ

Joe, you really need to quit while you're behind because you keep digging the hole deeper.

In short because "absolute chamber pressure is what is wanted" a strain gauge can't give you that,

Excuse me? The CUP method only gives that and it is called "peak pressure". A strain gauge and transducer with give not only the peak pressure but the time/pressure curve of each shot. That is something CUP can not do.

they are advised by their legal team not to use the strain gauge solely for publishing reloading data.

To quote from the movie; "who is they"? The ammunition industry is quite large so could you be specific by naming the companies and how you got that information? I ask because I know of several that use the M83 Oehler in testing and developing their product and their data.

A strain gauge also needs a verified pressure to calibrate it.

Joe, you really must do a little more research as your lack of knowledge here is getting embarrassing. Strain gauges are "calibrated" at manufacture. With each gauge you get the "calibration data" that is inputted into the program. The copper crushers of the CUP system also must be "calibrated". You get a tarage table with them and without that you can not measure the crush and determine the pressure. Piezo transducers also must be calibrated (quite often actually) before use. Additionally "reference” ammunition is used to verify velocity and psi readings. A discrepancy between what the reference ammunition is supposed to have and what the test fixture records is called an "off set". That off set is then added or subtracted from the test fixtures readings to give the supposed psi and velocity. This is because all test fixtures are different, same as all guns are different - even in the same cartridge.

One thing a strain gauge can do that the others cannot is "duh" tell you the stress or strain of the metal that it is attached to. The other methods cannot tell you that.

You finally got something that is correct. What the relevance is escapes me however.

Two very knowledgeable men in this field have an on going argument over chamber pressure. The says what is important is what the brass (the case) can take and let go at.

No real argument there; the fact is that modern brass cases can contain pressure before showing any measurable expansion to a much higher degree than is safe for many actions. Secondly many times the cases do not expand until the psi gets into a gross over pressure or proof load situation. I recently tested some Winchester .223 M193 ammunition. The average peak psi was 65,700 psi. There was also an attendant 200+ fps gain in velocity. Obviously that is a bit of an over load yet there was no measurable case head expansion. That kind of "fact" is all too prevalent when using CHE. CHE is no longer an acceptable method of pressure measurement because it is unreliable. BTW; if using CHE how does one "calibrate" the lot of cases used to know what any measurable expansion means in psi?

Lastly I would ask you or anyone; where in the world, locked away in some government vault, is a standard one pound per square inch? What is the standard? Well, there isn't any. One psi is calculated or measured by testing the effect of pressure on something.

All psi measurements, CUP, transducers, strain gauges and questimations such as "Quickload" are all computations. The differences are “equivalencies" as such. None are "absolute" and all very to a degree. What Remington gets with .308W "reference" ammunition in their test barrel is going to be different from what Winchester gets, what Federal gets and what you and I get in our commercial barrels. That is why ammunition companies and now most loading manuals give data that follows SAAMI guidelines concerning MPLM (MAPs), MPSMs, and MEVs in load development. The use of Peizo transducers and strain gauges now allow that because they give a much better and complete picture of the time/pressure curve where as the older CUP method does not. Most factory ammunition is loaded below the SAAMI MAP (MPLM) for that cartridge contrary to most everyone's belief that they are all loaded to max psi. For example, the MAP (Maximum Average Pressure) for the .308W is 62,000 psi. I have yet to find a factory round that hits that average psi.

So Joe, I suggest you do a lot more research or get some hands on experience with a properly set up strain gauge machine to measure firearm psi such as an Oehler m43 or M83. If you do that then you might have some knowledge of what you speak. Now you don't and continue to post erroneous information and assumptions. You know what happens when you "assume" because that's what you're making yourself look like.

Larry Gibson

Not so Larry, yeah the device itself is calibrated, but then you have to deal with the electronics that it connects too. The two guys I was talking about have worked with your famous Oehler. The strain gauge does do the time dwell as you said. The one guy is a physicist and I believe he knows more about it then you. There has been a long going fight between the strain gauge and other devices and what they are measuring. The strain gauge can't measure the chamber pressure because it's not placed in the chamber like the others. It measures the strain on the metal which then it has to calculate from there.

At any rate I'm finished. I know how it is to argue with you ....ever lasting eternal I'm not going to do it. So go ahead and waste your time with your rebuttal, I'm gone and finished on this subject.

quote:

Originally posted by SmokinJ:

At any rate I'm finished. I know how it is to argue with you ....ever lasting eternal I'm not going to do it. So go ahead and waste your time with your rebuttal, I'm gone and finished on this subject.

this is called the quit and runaway method of finishing an arguement.

Joe - You are dead wrong - period, full stop. Oh, you may have bits and pieces correct, but your thrust (pun intended) is wrong.

there's NOTHING illegal about a strain gauge.. and you can't begin to backup what happens in a company's legal department... also, ther's no nato container.. or UN container.. there's just a different marking for the new laws.

big deal...

now, if you are done, I think we've corrected your internet rumor enough at this time.

quote:

Originally posted by jeffeosso:

quote:

Originally posted by SmokinJ:

At any rate I'm finished. I know how it is to argue with you ....ever lasting eternal I'm not going to do it. So go ahead and waste your time with your rebuttal, I'm gone and finished on this subject.

this is called the quit and runaway method of finishing an arguement.

Joe - You are dead wrong - period, full stop. Oh, you may have bits and pieces correct, but your thrust (pun intended) is wrong.

there's NOTHING illegal about a strain gauge.. and you can't begin to backup what happens in a company's legal department... also, ther's no nato container.. or UN container.. there's just a different marking for the new laws.

big deal...

now, if you are done, I think we've corrected your internet rumor enough at this time.

Jeff....send me your email in pm and I'll send you some links and data. Unless you can tell me how to send PDF files in pm's.

Joe

None of the other methods are "placed" in the chambers either. Some use a hole drilled in the case and others have to deal with gas leakage around the hole in the case or how much psi it took to cut the case where the hole was before the transducer was pushed on. Lot's of variable to all, that's why it was referred to as an "equivelence" by me in stead of the "absolute" you used. There are no "absolutes". All the other methods also have to "deal" with the same "electronics" so pray tell, what is the difference?

When you say "your Oehler" it is obvious you've just let jelousy over rule any common sense or intelligance you might make in this discusion.

As Jeff has told you; "You are dead wrong"

Probably good, considering you're lack of knowledge and personal feelings involved, that you've decided to back out of this discussion.

Larry Gibson

There is no fight between strain gage and other pressure estimation techniques. None can measure chamber pressure directly without disturbing the pressure event. They are all estimates; each technique has its own set of warts and its own advantages. We can't evaluate the absolute accuracy of any technique because we don't know the "truth" for comparison.

KenO

quote:

Originally posted by KenOehler:
There is no fight between strain gage and other pressure estimation techniques. None can measure chamber pressure directly without disturbing the pressure event. They are all estimates; each technique has its own set of warts and its own advantages. We can't evaluate the absolute accuracy of any technique because we don't know the "truth" for comparison.

KenO

Thanks Ken I'm sure everyone appreciates your input, I know I do.

I started this with what I thought was a fairly simple & straightforward question about a formula for calculating pressure. It has evolved into highly technical discussions of pros and/or cons of one sort or another. Not where I intended to go.

I was not concerned with calculating/measuring pressure to avoid a blowup. (One guy made an issue of my use of the term calculate vs measure; what's with that? Someone else corrected him.)

If there is a fairly simple formula/equation to arrive at pressure readings I wanted to know what it is. I gather there is NOT a simple formula.

Now, for those who questioned and or criticized the question, here is my reasoning. When I start load development, after selecting a bullet, I go to a manual, or several, to pick a powder. Usually, I start with a powder
recommended by the manuals, but they do not all agree on the best powder. They vary, depending on their test results, as you all know. However, there is some uniformity as they usually include the same powders. And, presumably, they are safe for most guns, with limitations, or they would not be published.

The Lyman Handbook lists, for .300WM, a 180gr Sierra wi RL22 @ max. vel. of 3017fps & pressure 50,300 CUP. This powder is recommended in several sources as a best powder, or one of the best. However, it is not listed as the best in the Lyman Book. Their best is N560.

Another powder, recommended in Lyman's
"Comments" section, is H-4831 wi vel. of 2938 but it does not show a pressure reading. Now, can I decide which powder to try without knowing the pressure of H-4831? Certainly can, but it would be nice to know; just one more bit of info to help in the process.

Also, should not have to say this, but I know enough to work up loads gradually & look for signs of pressure. I am not inclined to exceed max. One of my guns, M98 FN Mauser starts showing pressure signs about 1.5-2.0 gr below max.- and I still get vel. exceeding max. listed. Sorry this is so long but I felt like the subject needed clarification.

i think, for your piece of mind, quickload would be a good answer

quote:

Originally posted by KenOehler:
There is no fight between strain gage and other pressure estimation techniques. None can measure chamber pressure directly without disturbing the pressure event. They are all estimates; each technique has its own set of warts and its own advantages. We can't evaluate the absolute accuracy of any technique because we don't know the "truth" for comparison.

KenO

Well I tried explaining all that but to no avail. I do wish, somehow, you could get your comparative test published. While we may not know the "truth" it is a very good example of what you refer to as "equivelence" between the different types of test methods. I'm sure it would also be an "eye opener" to those who have difficulty understanding the the different pressure measuring methods. Always good to hear from you.

Larry Gibson

quote:

Now, can I decide which powder to try without knowing the pressure of H-4831? Certainly can, but it would be nice to know; just one more bit of info to help in the process.

I think you need to relax a bit. You can have information overload.

The point is that it is not necessary to know the exact pressure your load develops. It is only necessary to recognize the tactile, visual, and measurable signs of reaching maximum pressure for your particular rifle and load properly to remain safely under that threshold.

It has been pretty well established that you can't calculate chamber pressure by the use of a simple formula...

And...it has also been pretty well established that the different ways of measuring chamber pressure gives useful data...

And...if you consult several reloading manuals, whether or not the pressure is given, you can pretty well bet it WON'T be over SAAMI specs for that particular caliber AND it will most likely come from different length barrels shot in different rifles.

AND...of course, everything in this sport is argumentative and there are plenty who jump at the chance to start a ruckus, large or small.

The upshot is...it doesn't really matter where the data came from as YOUR rifle will be different and it is YOUR rifle you are dealing with...

As you've all ready seen that one of your rifles is comfortable with less powder.

I have rifles that WON'T handle max loads for a specific caliber without the bolt locking up and WON'T hit the velocity published in some manuals...

I have several rifles with long throats that I seat the bullets out well beyond "SAAMI" specs, that will handle several grains ABOVE max powder amounts and hit velo's above published numbers...with no pressure signs and good case life.

And I have a few rifles that I won't go anywhere NEAR max loads....leverguns and early military mauser actions.

Chrono's are relatively cheap and will give you velocities which you could compare with published data that does have pressure data and get a close approximation of your chamber pressure...but it is only an "approximation" and it is the velocity you are more interested in anyway unless you start stepping on the wild side.

Academically speaking, I like to know, generally, what the pressures might be, but unless I'm working on a load for a wildcat I just built and I use a software program to predict pressures so I know where to start and stop...pressure in these cases are only a sidebar.

I think it was a good question...I'm also sure there are many who would also like to know if such a formula was available but just haven't asked.

Luck

quote:

Originally posted by olguy:
...If there is a fairly simple formula/equation to arrive at pressure readings I wanted to know what it is. I gather there is NOT a simple formula. ....

That is correct, there is not a simple "Firearm Pressure Formula".

As long as you do not use CHE & PRE, then you are only guessing if the Pressure is too High for the Case. For people who do not understand this, the Case is "weaker" than the firearm. And Cases vary in strength from Lot-to-Lot and from Manufacturer-to-Manufacturer. So, estimating Pressure with any Method other than CHE & PRE puts you into either a Destructive Test Mode(The Case is destroyed) or you are typically getting Haphazard, Non-Calibrated, Fudge Factored, Guessed At, Second Hand information, and you still don't know how the Case is responding to the Pressure.

Strain Gauge Fiascos are the most misleading and totally worthless devices ever offered to Reloaders. They work fine in Lab Environments for rough Pressure Estimations, once they are Calibrated to a Known Standard. Way too many variables and the need for a complete System Calibration with a Known Standard for them to do anything but mislead people outside a Lab. You can see that within this thread.

CHE & PRE work and work well for estimating the most important aspect of Reloading - what is happening to the Case. ALL OTHER METHODS are as useful as obummer, clinton, schumer, boxer, and pelosi to the Reloader.

quote:

ALL OTHER METHODS are as useful as obummer, clinton, schumer, boxer, and pelosi to the Reloader.

I do love the logic on AR so !

We are to measure by hand a spot on a tapered cilinder, using a 4 decimal or 5 decimal capable hand hand held measuring instrument before and after a single firing and that in itself has an accuracy of how much?

Futhermore a single measurement of a system that is almost entirely stochastic, A sample of exactly one ! on a spot determined how?

And to boot it is not that we are to be using the same brass cilinder over and over and subjecting it to a variation of pressure impulses is it now?

Is this measuring device mounted in a jig that ensures that the measurer measures the same spot on the taper exactly ?

Measuring the response of a cilinder of brass that is hardly precision made and this is somehow "better", wait I will paraphrase less haphazard, Non-Calibrated, Fudge Factored, Guessed At, Second Hand information" , and somehow you do know how the Case is responding to the Pressure ?

Perhaps i'm missing something here ?

quote:

Originally posted by Hot Core:

quote:

Originally posted by olguy:
...If there is a fairly simple formula/equation to arrive at pressure readings I wanted to know what it is. I gather there is NOT a simple formula. ....

That is correct, there is not a simple "Firearm Pressure Formula".

As long as you do not use CHE & PRE, then you are only guessing if the Pressure is too High for the Case.

I agree but will assert that there are "WAG" and "SWAG" guesses.

Some information can be available to help with the guesses.....still a guess but pieces of the puzzle are available to an experienced reloader.

I'm a believer that "quickload" can give strong hints about pressure as can velocity....while misreading the evidence can be a gross error, the savvy reloader can often get the data he needs.

That said....."case head expansion" is still among my pieces of data.....not for pressure so much but for answering the question "Is this load safe for the components I'm using in my gun?"

BTW...WAG = wild ass guess

SWAG = scientific wild ass guess

As usual HC has given us his usual speal on CHE/PRE by denigrating all other methods.

I have to agree with him that using CHE takes you to the limits of the cases ability to handle the pressure. It doesn't give you any indication what the pressure is though. But what if the action you are using isn't for such pressures? What if you use different cases that can't handle the pressures the other cases could? It's probably not going to be "good" things that happen.

The OP asked about calculating pressures. Quickload is as good as any but as mentioned there are many variables that affect pressure. This is why there is no "absolute accuracy" in any method because we don't know the truth or what the real pressure is for comparison to paraphrase Dr. Oehler.

What we do know is that what is a "maximum" load in one rifle may not be in another or it may be over maximum in another rifle. If we stay with proven practices to work up a load and use all available methods we can stay out of over pressure areas and enjoy shooting without worry. That is why it is important to work up loads for you particular firearm.

Do we need to know the exact pressure? It’s probably not. Most of us go blissfully on our way never really knowing. HC has no idea using CHE/PRE because he doesn't have any idea of the "calibration" of the expansion of the cases he uses (he always likes to mention "calibration" so I thought I'd remind him). Those who stay within the loading manual data and use other pressure signs when working up loads are estimating that the pressure is safe but they still don't know what it is. Those who use chronographs and load data also don't know what the pressures really are and are estimating. Those of us who use strain gauges or perhaps even a transducer are still only estimating because, as Dr. Oehler mentions, we don't have the "truth" for comparison.

How do we really know that “reference ammunition” is really the pressure it is measured at? We don’t know. What we do know is that in an accepted test fixture it measured some pressure. We then simply have only that pressure for comparison. Is it safe? We do know if such a load is 60,000 psi for instance and loading higher the primers loosen and/or blow at 70,000 psi then we assume the 60,000 psi to be safe. It is assumed all other loads at 60,000 psi in that test fixture to be safe also. Since we aren’t using that test fixture is the reason all loads we use should be worked up to in the firearm they are used in watching for pressure signs. Probably best to stay within recognized loading data for most of us.

Do we "need" to know the velocity and pressure to shoot? No, but in some instances its "nice" to know and provides us with additional information we can use. The OP simply wanted to know if there was a method to calculate pressure and there are several. The older Powley Slide computer was useful (I still have mine) and now there's Quickload. Both are useful but still only estimations like any other method. The industry uses CUP, Piezo transducers and strain gauges to develop and test load development and ammunition with. Those methods are the recognized "standard" today. Are they absolute"? No they are not but they are the best methods we have so far.

The pissin’ match part of this discussion was because SmokinJ said it was "illegal" to use strain gauges in load development because they were inaccurate. To bad we drifted from the OP's original question but Joe's misleading and untrue statement needed to be addressed.

Larry Gibson

Other then curiosity why would it be necessary to calculate/compute pressure? Safe handloading practice behooves one to remain within the maximum recommended charges listed in the load manuals. Personally I'm not that daring to go over max nor have I ever felt the need to do so. I guess I'm just anal and prefer accuracy to velocity and always seem to find an accuracy charge somwhere less then max.

Unless you are venturing into the unknown by exceeding maximum charge listings pressure shouldn't be that important, should it? I suppose if you are developing a new wildcat knowing the pressure would be important to determine a reasonable and safe maximum charge. In that case I would prefer an actual measurement via calibrated device rather then a calculated estimate. I seems to me there are too many variables to safely calculate pressures or am I wrong?

Hotcore gave the best reply here over everyone one including Ken Oehler.....just as I've been trying to convey....no major manufacture would solely rely on strain gauges for figuring or publishing data because they "can" be inaccurate enough to present a problem.

Now let's see you screw that reply up Larry and here is what Hotcore said you have parameters to go by:Strain Gauge Fiascos are the most misleading and totally worthless devices ever offered to Reloaders. They work fine in Lab Environments for rough Pressure Estimations, once they are Calibrated to a Known Standard. Way too many variables and the need for a complete System Calibration with a Known Standard for them to do anything but mislead people outside a Lab. You can see that within this thread.


Clem, to answer your question..because Larry Gibson has to always be right.

Ok Joe, you win. There does that make you feel better......

Larry Gibson

Alf just said a mouthfull...he must have been reading my mind..or maybe it is great minds think alike.

Most of the rest is just personal opinion, little boy pecker waving and "I'm smart, your dumb" KRAPOLA.

While a large amount of the information might have a modicum of truth...it is still pretty useless when it decends into "my dog is bigger than your dog".

As far as QL or Load from a Disk...they both use pressure formulas or comparisons to come up with their pressure numbers...the numbers are NOT accurate over the caliber/case range and they were never designed for anything other than a "STATISTICAL GUESS" for velocity/pressure.


I have Powley "stuff" going back to the cardboard "slipstick", several different copies of early Powley computer programs and a couple I coded myself, PLUS at least two from present day online sources. QL is probably the best, having most of the newer powders, bullet, cartridges, etc. They all do the same thing...JUST GUESS, EDUCATIONALLY SPEAKING.

AND the data doesn't mean squat, depending on how far from the "middle weighting" the statistically derived data is.

Jesus...quite blowing smoke and strutting around...

By the way...NO ONE KNOWS FOR CERTAIN, UNLESS YOU WORKED IN A/THE TESTING LAB FOR THE SPECIFIC MANUFACTURES PRODUCTS, JUST HOW THE DATA WAS DERIVED...ALL YOU CAN DO IS "GUESS"...which is what is going on anyway.

Luck.

Clem

To answer your question let me give you an example, not because "Larry Gibson is always right" but because it is the "why" sometimes. BTW; just for clarification, I've been wrong in this game numerous times but I try to at least learn from my mistakes.

Recently, on another forum, I've been posting some information on Leverevolution powder loads in a M94AE 30-30 with a 24" barrel. I've a strain gauge attached and use the M43 to measure the pressure and velocity with it. Understanding that the data recieved from such tests (as in all other tests with whatever test equipment is used) needs to be compared to something I used as a "reference" for "comparative" data 10 shot strings of 12 different factory 30-30 loads including the Hornady 160 FTX LeveRevolution ammuntion. I also have SAAMI's data for the cartridge. All the factory ammunitions pressures as measured with the M43 using the M94AE were within the SAAMI specified data as it should have been.

Now, contrary to what some may think here, when you have a sample of 12 different factory rounds for comparison you have something to safely measure/compare against. I might not be able to say for certain that the psi was, in fact, 38,400 but if the M43 measured psi of the factory ammuntion was 39,100 psi(M43) and my loads measured 38,400 psi(M43) I could be pretty sure my loads were "safe" and at an acceptable pressure level for my M94.

In the 3 part test I was developing a load for a 150 gr jacketed bullet of which there was some loading data available. The other bullet, a Lyman 311041 cast bullet of 177 gr, there was no data using LeveRevolution powder for. I also was testing what was supposed to be a "hot" load of Winchester 760 under the RCBS 30-180-FN cast bullet.

Since LeveRevolution isn't a powder used by the Powley Slide computer it wasn't of any use. Also I couldn't find where Quickload applied to Leverevolution powder using a cast bullet either eliminating that. Use CHE/PRE?, not hardly as the M94AE's action strength is way below the point where any meaningful "pressure" measurement of case head or expansion ring would be found. So what to do?

I followed standard loading practices and reduced the starting load proportionally to the heavier 177 gr cast bullets weight and worked up the load. I would have been ok by using a chronograph and watching for any stiffness in opening the action but frankly the improved velocities may have made me stop early on because the pressure should have been getting pretty high for a M94 action based on normal powder use at the velocities I was getting. What I found with the M43 strain gauge attached to the M94 was the pressure using a 100% load density of LeveRevoltion still gave less pressure than the Hornady factory LeveRevolution ammunition and less pressure than 2 other factory loads. I also gained 200 fps over a similar pressure load using 4895 powder with that bullet.

That's just one reason where a proper estimation and the measurement of pressure against a known measurement (the 12 factory loads) can help us with our load development. Powleys computer, Quickload, HCs CHE/PRE and even the judicious use of a chronograph (for comparative purposes - not to "measure" the pressure) would not have helped. As you can see I was not "guessing" as has been suggested, I was actually measuring and comparing against a measured (with the same equipment) standard (the factory ammunition). There are other reasons but I'm sure you grasp the jist of it with the one reason presented.

BTW; the "hot load" with the 30-180-FN was found to have less pressure than 3 of the factory loads and was well below the SAAMI MAP of 42,000 psi. Again, not a "guess" but an actuall measurement against a known standard.

Larry Gibson

quote:

Originally posted by Larry Gibson:
Clem

To answer your question let me give you an example, not because "Larry Gibson is always right" but because it is the "why" sometimes. BTW; just for clarification, I've been wrong in this game numerous times but I try to at least learn from my mistakes.

Recently, on another forum, I've been posting some information on Leverevolution powder loads in a M94AE 30-30 with a 24" barrel. I've a strain gauge attached and use the M43 to measure the pressure and velocity with it. Understanding that the data recieved from such tests (as in all other tests with whatever test equipment is used) needs to be compared to something I used as a "reference" for "comparative" data 10 shot strings of 12 different factory 30-30 loads including the Hornady 160 FTX LeveRevolution ammuntion. I also have SAAMI's data for the cartridge. All the factory ammunitions pressures as measured with the M43 using the M94AE were within the SAAMI specified data as it should have been.

Now, contrary to what some may think here, when you have a sample of 12 different factory rounds for comparison you have something to safely measure/compare against. I might not be able to say for certain that the psi was, in fact, 38,400 but if the M43 measured psi of the factory ammuntion was 39,100 psi(M43) and my loads measured 38,400 psi(M43) I could be pretty sure my loads were "safe" and at an acceptable pressure level for my M94.

In the 3 part test I was developing a load for a 150 gr jacketed bullet of which there was some loading data available. The other bullet, a Lyman 311041 cast bullet of 177 gr, there was no data using LeveRevolution powder for. I also was testing what was supposed to be a "hot" load of Winchester 760 under the RCBS 30-180-FN cast bullet.

Since LeveRevolution isn't a powder used by the Powley Slide computer it wasn't of any use. Also I couldn't find where Quickload applied to Leverevolution powder using a cast bullet either eliminating that. Use CHE/PRE?, not hardly as the M94AE's action strength is way below the point where any meaningful "pressure" measurement of case head or expansion ring would be found. So what to do?

I followed standard loading practices and reduced the starting load proportionally to the heavier 177 gr cast bullets weight and worked up the load. I would have been ok by using a chronograph and watching for any stiffness in opening the action but frankly the improved velocities may have made me stop early on because the pressure should have been getting pretty high for a M94 action based on normal powder use at the velocities I was getting. What I found with the M43 strain gauge attached to the M94 was the pressure using a 100% load density of LeveRevoltion still gave less pressure than the Hornady factory LeveRevolution ammunition and less pressure than 2 other factory loads. I also gained 200 fps over a similar pressure load using 4895 powder with that bullet.

That's just one reason where a proper estimation and the measurement of pressure against a known measurement (the 12 factory loads) can help us with our load development. Powleys computer, Quickload, HCs CHE/PRE and even the judicious use of a chronograph (for comparative purposes - not to "measure" the pressure) would not have helped. As you can see I was not "guessing" as has been suggested, I was actually measuring and comparing against a measured (with the same equipment) standard (the factory ammunition). There are other reasons but I'm sure you grasp the jist of it with the one reason presented.

BTW; the "hot load" with the 30-180-FN was found to have less pressure than 3 of the factory loads and was well below the SAAMI MAP of 42,000 psi. Again, not a "guess" but an actuall measurement against a known standard.

Larry Gibson

Aw hell Larry, don't change because of me. I've been use to you that way for way over 10 years.

I've been following your Leverevolution tests and they are very good. I've hearing lots of good things about that powder and now hearing it from you and your testing. Now it would be interesting in seeing what that does in the 7.62x39 and would appreciate you testing that especially with the Lee 155 grain cast. That powder may open up a whole new avenue for cast shooting. See what you have gone and done now...I have to go out and buy some.

quote:

Originally posted by olguy:
Not a newbie, but still learning. Recently, I again read that when developing loads, to start by selecting two or three powders which give highest velocity and, preferably, yield low, or lowest, pressure.

However, only two of my loading manuals provide pressure: Hodgdon's 2010 Annual Reloading Manual and Lyman's Reloading Handbook, 48th Ed. But, they do not include all powders. Hodgdon appears to show readings just for its propriatary powders: Hodgdon, IMR & Winchester. And, Lyman gives pressure for most of loads but omits some.

My other manuals: Barnes, Nosler, Hornady, & Speer do not provide pressure entries. Wouldn't you know, a couple of powders I was considering did not yield pressure entries.

I understand there are programs (and instruments?) which will provide the info. But, is there a way to calculate pressure, like a formula? Without explaining why, I prefer
not to spend the money for programs or instruments, etc., at least at this point.

In a word NO. There is no way to predict or calculate pressures. Even the data given is only valid in that test platform & your rifle/handgun will certainly vary. There are pressrue signs & one should learn to read them & pay attention to them as a reloader.

I guess I have not done a good job of explaining what I was seeking, or why. So, I will try again. This is not about exceeding max pressure and the potential disaster resulting therefrom. It is about selecting a powder for working up a load.

As I earlier indicated, some sources recommend selecting a powder that provides highest velocity and, preferably, low pressure. Only two of my load manuals provide pressure readings. But entries for all powders are not stated. (Interestingly, Lyman entries are psi for some and CUP for others.)

I was hoping there would be a way of calculating/measuring pressure for a potential powder in advance of selecting and using it. Now, before jumping all over me, I would advise you all of something one of my college profs told me years ago: "The only dumb question is the one that never gets asked." Also, I am not an engineer, physicist, etc.

If there was a simple formula/equation that I could use to calculate pressure for purpose of selecting a powder- then I would use it. Is it mandatory? No. I can keep on doing what I, and probably most others have been doing. Just pick a powder and try it.

FOOBAR & Larry: Thanks for your replies; you two seem to get it and have been of the most help in addressing my question.

Clem: You missed it. I never suggested exceeding max charges in the load manuals. How do YOU select a powder? What if, as is often the case, there are several good powders listed? Do you not think about pressure as a factor? I again recently read of a writer (Ross Seyfried) selecting a powder based on high velocity which he also noted had lowest pressure of several he considered. (I have also read this elsewhere.) Was he wrong in emphasizing that?

Yes, I am aware of pressure signs, how to read them- and paying attention to them. (See my June 10 post.) I am also well aware of variances in guns and the need to work up loads from scratch for each individual gun.

Maybe the problem is that, when I started this subject I said I was not a Newbie but still learning. I meant that, in the sense that we are all, or should be, life long learners. I'm 75 yrs young, college educated, retired from a successful career- and if there is anything I have learned it is that there is a heck of a lot that I have not learned.

If that's all you need and no pressures are listed in your manual, then just pick the slowest powder recommended in the reloading manual (check the burn rate chart) for the bullet weight you want to load.

It will generally have the lowest pressure.

You can also check online data direct from the powder manufacturer. It has pressure data.

What cartridge, bullet combo are you loading? I don't see that in the OP.

quote:

If there was a simple formula/equation that I could use to calculate pressure for purpose of selecting a powder- then I would use it.

Here is the Powley version of a pressure calculator. Be sure to read it's limitations.

olguy

rcmuglia's suggestion is the simplist and best way to avoid any problems. However i will suggest another method that I learned form several gun writers of old. Yes I know most have a bad rep about not knowing anything but occasionally they get it right. This is one of those times.

Most manuals will list loads for any cartridge by powder burning rate, slow to fastest or visa versa. If you know any of the max loads will be compressed loads don't use those. Pick those from a recent manual that give the best loading density, usually the middle ones. Determine how many gr of powder in tenths of a gr are used form the listed start load to the maximum load. Then subtract the start velocity from the max velocity and then divide that by the tenths of gr of powder it took to get there.

That will tell you the approximate fps gain per tenth of gr of powder increase used. selecting the powder that gives the highest fps gain per gr of powder with close to or at 100% loading density will most often give the most efficient powder for that cartridge with those componants. That method of powder selection can give you will give you a safe powder that will probably give excellent results in your firearm. Since i started using that method I've always had excellent results with accuracy and velocity while staying within safe psi parameters.

Again though, as rcmuglia mentions, using the slowest compatable powder for the cartridge will give the lowest pressures but most often not the highest velocity.

The loads in most all recent manuals do not exceed SAAMI pressure MAPs for a cartridge so if you work up the load with a powder selected as I've mentioned, watching for pressure signs in your firearm and not exceeding the max load you will, most of the time, be okay and get the maximum performance for the cartridge.

Larry Gibson

The strain gauge is dumb all it can tell us is
the strain in the location it is attached.
The pressure/stress calculation is based on
a long constant diameter cylinder. Stress flow
is not unlike water flow they are concentrations
at discontinuities. however the ratio between the local stress and actual pressure is constant
so that readings may be compared between loads.
The use of a factory load to verify is an appropriate term.
The NRA loading manual has the formulas
for calculating press ure if you know te velocity. It is a PIA.
The basic reason for measuring is safety, and
since the case is the weakest link indications
that is begining to yield is very important.
I think that Smoking overheard a conversation
on stress flow and missunderstood.
Good luck!

quote:

Originally posted by Clem:
Other then curiosity why would it be necessary to calculate/compute pressure?

For the Reloader it is not necessary at all. I agree with Vapo that the Software Programs available today will "guesstimate" the Pressure as close as ANY Haphazard, Non-Calibrated, Fudge Factored, Guessed At, Second Hand Information, worthless Strain Gauge Fiasco.

quote:

Unless you are venturing into the unknown by exceeding maximum charge listings pressure shouldn't be that important, should it?

The problem here is unless the person is using the always reliable, never fail, totally repeatable, time tested CHE & PRE, he really doesn't know if Exceeding "maximum charge listings" is Safe or not.

quote:

I suppose if you are developing a new wildcat knowing the pressure would be important to determine a reasonable and safe maximum charge. In that case I would prefer an actual measurement via calibrated device rather then a calculated estimate.

Especially on Wildcats where no Factory Tested, SAAMI Spec Data exists, the ONLY THING that works is CHE.

quote:

I seems to me there are too many variables to safely calculate pressures or am I wrong?

Due to the variables in the Chamber Dimensions, Barrel Dimensions and all the Lot-to-Lot variables in the Cartridge Components, there will never be totally Accurate Calculated Pressures that apply to ""ALL"" Firearms chambered for the same Cartridge. It is possible to guesstimate the results, but it is not realistic to believe it applies to ALL firearms chambered for the same cartridge.
-----

A Haphazard SGS=Reloaders Pyrite(aka Fool's Gold)

quote:

always reliable, never fail, totally repeatable

In these few words lie the problem !

And then for the best in internet humour and logic !

"Due to the variables in the Chamber Dimensions, Barrel Dimensions and all the Lot-to-Lot variables in the Cartridge Components, there will never be totally Accurate Calculated Pressures that apply to ""ALL"" Firearms chambered for the same Cartridge. It is possible to guesstimate the results, but it is not realistic to believe it applies to ALL firearms chambered for the same cartridge.

And this does not apply to the brass ? Perhaps if not the most inconsistant of all the components used.

quote:

Originally posted by ALF:
And this does not apply to the brass ? Perhaps if not the most inconsistant of all the components used.

Could not possibly be happier that alf posted his last bunch of total ignorance. It proves EXACTLY what I've told you folks all along - alf has no clue about Reloading nor understanding how Pressure works in a firearm.

Ah HC !

I confess, I know nothing, nothing at all..... so once again, and with baited breath I would humbly ask, why not explain to us lowly folks here on AR how does pressure work in firearms?

I'm sure there are a number of us who would like to know

And I would personally ask for you to explain to me how plastic deformation of brass is correlated to pressure seeing as the individual pieces you are measuring are likely the least uniformly constructed component in the whole chain....... and do remember it was you that said: Always reliable, never fail, totally repeatable

With regard to the above about brass:

Norma brass is softer than PMP and Lapua brass for example. Norma brass is generally also thinner and more sensitive to higher pressure levels and as such it has been reported on other gun forums that they are more susceptible to primer pocket expansion.

I would not waste my time with PRE and CHE, as we have been reloading for years safely without the 'technonlogy' of PRE and CHE. That means I can do without it.

Here is a typical story from 24 Hour Campfire:

"I shoot 1000yd BR and use the 6.5/284. Primer pockets getting loose is a hassle. I have found Lapau brass to do better then Norma. 3 loads in Norma and the primers will fall out. I can get 4 or 5 in Lapau. When loose I throw the brass away. Last year I went thru ~650 Norma cases. This year I'm back with Lapau." --- LRF

Some interesting info:

http://www.angelfire.com/ma/ZERMEL/caseheads.html

Warrior

Variation, unscientific testing procedures, non-uniformity (which is a piece of variation) and a ton of other "things" is the conundrum of making ANY general statement about what you can do with software programs, pressure testing equipment and chrono's.

No matter HOW you go about doing your test and Larry's example is an excellent way to do it and is basically how we did it in the old days(pre chrono in everyones tool kit)...the data is STILL only good for a specific set of parameters and not necessariyly transferable to the rest of the population(of guns or components or people).

The problem being the information is highly argumentative and open to interpretation and personal bias, and use by individuals who DON'T know the full ramifications.

Not to cast dispersions...but ANYONE with the green to buy a shooter and can read, no matter how badly or from another country with problems of translation and idioms, and has access to ANY AND ALL THE BS or hot air blown about on the net, for whatever the reason, pecker waving - information - good intentions or bad!!!...can use WHAT they read for good or bad.

THAT IS THE PROBLEM.

As you can see just in this thread alone there is a large amount of INTERPRETATION AND MIS-UNDERSTANDING, of defensive and offensive posturing, "proofs" - good or bad, good information, questionable information, etc., going on.

Larry's way of going about "testing" is one of the better examples and is what someone with good equipment can use to get a good "guestimate". EVERYONE "could/should" do it that way, but "HOW MANY" will/would??

There is no question about proper procedure, just the level to which the "average" reloader will go to. How far will the once a year hunter go to "test" his reloads...a newbie deciding to jump over something they don't quite understand and is infinitly important, or getting lost in translation.

Very few ever think about those ramifications or even care when it comes to "defending their postition" on the net or anywhere else for that matter. The worst hoohaa's I've read are over hair splitting and defending a position than anything else...filled with nuances pretty much worthless as far as the original questions are concerned or to the average shooter.

Everyone responding to this link has hit just a few of the variation problems, but each is talking to the other members of the choir and not really to the rest of the world. Most of us live in our own small world and forget the web is so large.

If we use the equipment we have, to determine what is safe for the individual shooters used in the testing process and then be CERTAIN that the equipment is certified as accurate by some "Standards" entity, THEN...maybe...the data is useful for extention to other shooter.

My example...I have two chronos...one Oehler 33 and a Beta Chrony...there is ~100-200 fs DIFFFERENCE in velocity testing one behind the other ~1 ft apart so they both are testing each individual round...depending on the velocity...doesn't matter WHICH one is in front.

Because I can't refire the same round twice, I can't change positions and retest to see WHAT the acutal variation is...but the Beta always test faster...this is using weapons from a pistol shooting 22 shorts to the highest velocity rifle I have in my rack...a 22-243 Midd shooting 35 gr VM's over 5000 fs.

WHICH data should I use...or should I average the numbers...or?? HOW many rounds actually constitute a statistically valuable sample of the population, how large is the population and WHICH population am I really testing...the chrono, the bullet, the primers - powder - cases - rifle...or am I just testing the temperature and barametric pressures at the time of testing or just the brand of the component?? WHICH is it??

Do you see now WHY I say it is just a "GUESTIMATE". No matter HOW we try to set up the test procedure, we end up testing multiple components, then generalizing to the larger population.

What everyone who has been doing this "stuff" for any length of time, who has studied ballistics and actually did testing in a meaningful way and bothers to post is saying is essentially true...for "THEIR" data population and shooters...but the data ISN"T true "UNIVERSALY"...the data is only statistically accurate/true as far as the small population is concerned...

Basically..."just guesstimates" in the broad sense..."generalities" no matter HOW you go about your testing...perfectly understandable by some and totally incomprehensable by others and worse...used incorrectly my most/many.

All we are doing is saying "Hey...I KNOW SOMETHING...THIS IS MY PROOF"...and "Oh, by the way whoever asked whatever the question was...here is the answer but I'm really telling .... he's full of ...., or "I totally agree", or "Yes, but you didn't cover a bullet 0.0000005" oversize will cause xxxxxxxxx pressure increase and blow you gun all to he**"

No matter...hopefully...everyone learns something new everytime they go online and that is the important thing.

Luck

quote:

As you can see just in this thread alone there is a large amount of INTERPRETATION AND MIS-UNDERSTANDING, of defensive and offensive posturing, "proofs" - good or bad, good information, questionable information, etc., going on.

FOOBAR,

This is the way life is ... and it is not going to change anytime soon. The best example is to decide who and what to believe ... the Democrats or the Republicans - they dish it up for us.

Hot Core will punt PRE and CHE even in the after life.

Warrior