Dumb Question:
Is there someplace u can get list of pressure's for firearms like u know do not exceed this so&so for So&so rifle or handgun.thanks. festus

Consult SAMMI if you don't want to wreck any of them, consult Clark if you want to keep em just below the "granade" threshold (for at least a couple of shots anyway)

If I understand what you're asking, it seems the best source of that information is a good handloading manual.

There are difference levels for different cartriges for different guns.
The info is not all in one place.
A magazine for the 4 levels of 32-20.
A web page for 4 levels of 45 Colt.
A load book for 3 levels of 45/70.

There are many more unknowns than knowns, and as Tailgunner points out, we should all stay ignorant and feel safe.

It would be terrible if someone wrote a book about this. I guess Ackley did, but it would be terrible if someone added to the knowledge.

Clark
I think your reading somthing into my comment that wasn't intended.
You have the most experance in distructive testing of firearms of any poster that I can recall, if anyone on this board can answer his questions it's you.
SAMMI limits are set for 100K firing cycles without structeral fatigue failure, not "how much will this design" take before premature failure is induced. Your work is on the other end of the spectrum, IE the structerial failure limit is X for brand A, .8X for brand B and 1.2X for brand C.
Personaly I find your methiodoligy to be sound, and your results interesting.
If I should choose to make use of your (or anyone elses) data, is my problem and responsability regardless of where the data came from origionaly.

quote:

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Originally posted by festus:
Dumb Question:
Is there someplace u can get list of pressure's for firearms ...

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Hey festus, The Hodgdon Load Manuals have a fairly good list as well as in the Introduction portion for a specific cartridge in the Speer Manual. I don't remember if Hodgdon has that info on their web site, but you could look there.

By looking for MAX Pressures, this seems to imply you have access to a Home Strain Gauge System. The HSGS devices have a LOT of inherent problems outside a recognized Ballistics Lab.

That said, there has finally been a poster on this Board (he goes by Lawndart or JCN) who finally figured out how to "properly" Calibrate a HSGS so it has some worthwhile use. If you happen to see him post, you might want to compare notes with him. JCN is the only person I've ever seen get it correct and that includes a few folks who "think" they know a bit about them, the folks that sell them and even the folks who actually manufacture them.

The reason the manufacturers don't go into detail about doing it is because it will be expensive and time consuming to get it done properly. But otherwise, it is just guessing.

Best of luck to you.

http://members.tripod.com/~cdk357/saami.html

The formating is screwed up at bit but you can figure out the correct values.

quote:

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Originally posted by festus:
Dumb Question:
Is there someplace u can get list of pressure's for firearms like u know do not exceed this so&so for So&so rifle or handgun.thanks. festus

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Actually, there are a number of sources for information such as you are seeking. However, it is not of much use for several reasons. One is that opinions of the amount of pressure a rifle can stand vary considerably. For example, it is often written that the Swdish Mauser action is suitable for pressures no greater than 40-45,000 PSI. Yet, any number of these actions have been rebarreled for cartridges like the .308 Winchester, and used for years with no ill effects. So such "pressure ratings" must be used as a guideline only (and "taken with a grain of salt" would be better yet!!). And, in most cases, it is better to err on the low side. I would never use an action like the Swedish Mauser for a .308 or a 6mm Remington, even though I am aware that this has been done without killing anyone.

Additionally, there are many currently-made actions for which no such figures have ever been provided by any reliable source. For example, what is the Max. PSI rating for the Ruger No. 1 action?

Thank you all for your input. gata check something out.app:
FESTUS

Great question Festus (and thank you for the kind words Hot Core),
El Deguello (great song BTW) nailed it.
Not to be too much of a smart ass, but if you are in doubt about a given firearm, don't go there.
There are two main reasons. First, metallurgy and heat treating in the old days was a very imprecise undertaking. Rifles, artillery pieces and naval cannons all blew up pretty frequently. Second there is no true and common understanding of what "pressure" in rifles really means. I won't go into a term paper on the subject, but all methods commonly used by ammunition and gun manufacturers to measure pressure only infer pressure indirectly. SAAMI measures it in the middle of the case, CIP measures it at the case mouth. Most importantly, the manufacturers don't calibrate their measurements against an absolute standard because their methods are unable to determine an absolute standard. I am not doing a good job of explaining this, but basically the best you can do is get a general range for a given gun.
Short of getting some expensive equipment (I just popped for another $2,000.00 worth of probes, hardware and software), the best thing you can do is get three good reloading manuals for cross referencing and use a good chronograph.
The SAAMI and CIP specs are written for the weakest rifles out there for a given cartridge. If you have a few specific rifle/cartridge combinations in mind let me know and we can walk through the process in this thread. The more I look into this issue, the more complicated it becomes. To know for sure what a given older firearm will handle you have to destroy the firearm. You will then know how strong it was, but the knowledge won't be of much use.
Clear as mud, eh?
JCN

Hey JCN, Always glad to give a fellow credit when he deserves it.

I was refering to the Thread where you mentioned your intent to Test some loads on your HSGS, record the results, send exact duplicate Loads to a recognized SAAMI Lab for them to verify, take their data and adjust the HSGS (I think you had mentioned Internal HSGS Chipmonks). Then the HSGS would be actually Calibrated to a known Standard and become a useful Strain Gauge System(SGS).

You are the first and only person who has ever posted in a Thread I've seen with enough "brains and common sense" to actually figure it out in 8-10 years of discussing it. And I've read lots of absolutely pitiful stuff on "How to Calibrate a HSGS."

By the way, since you will be Calibrating the System in that way, you really don't need to turn down the barrel shank. The JCN SGS Calibration Method will compensate for any small errors in determining Chamber Wall Thickness, which none of the other methods I've seen will do (even though the posters claim their method will).

Congratulations on figuring it out and best of luck to you and your lady.

Hot Core,
It gets better. To send one 12 round sample to HP White labaratories costs $482.00. Yep, $40.00 per round.

Sooooooo, I am saving my pennies this year and next to get a universal receiver and conformal piezo electric testing rig. If you can't afford to use a SAAMI lab then you just have to build one for yourself.

Hopefully there are enough other folks interested in just what their ammo really is doing to offset some of the start-up costs.

This way I can work up loads at a pretty fast clip with the Pressure Trace, and then run it through the monster when I think I am there. The math models indicate I should be able to get within 250-400 psi of the truth, and that ain't half bad.

Right now I am developing data for a new line of bullets for a client. It is kind of fun traveling without a road map .

lawndart


I still get the willies looking at 100 year old rifles, especially if they were built under wartime time and skill constraints.

Hey JCN, That seems to have gone up from when I checked (at least) 8 years ago. I think it was around $25/round back then. Been trying to think of the name of the Lab in Atlanta I talked to, but it has escaped me so far. Maybe Wylie(SP?)?!?!

I did so much work with LAW Engineering(Charlotte), they are the only people I can think of right now. But, they weren't a Ballistics Lab.

Once you get enough equipment and procedures in place, you should be able to become a Certified Lab just like the rest.

When you get it operational, there should be plenty of folks wanting to use your Lab as a Calibration Source for their HSGSs and turn them into useful SGSs. I believe there are a good number of folks on this Board who have an HSGS and "think" it is Calibrated, when in reality it isn't.

Anyway, I don't think I'll ever be able to properly explain how "GREAT" it was to finally see you post the correct way to actually Calibrate a HSGS. Some of the stuff posted on this and other Boards(and rumor has it in Articles) is so off the wall that it has been a constant source of amusement for me.

I guess a lot of that will stop now as I can reference the new folks asking about, "How in the world is it possible to actually Calibrate an HSGS?", to you.

Best of luck in getting it all set-up and operational. It seems to be one of those "nitch things" that has just been absent for the average Reloader.

Hi all
First of all thanks everyone.Guess i should explain what i wanted in the first place.In some reloading manuals they show loads lets say for 30/30 150gr bullet at x preasure's with x load of powder. Then next 150gr with dif powder & higher or lower preasure's ok! what im trying to do is find lowest preasure with the highest velocity witch some manuals show me. but what than is the highest preasure i should stay away from in all load's listed for that cal. not that it will help me much but was wondering i prety much stay with the loading manuals anyway but like to push it a little once in awhile lol. hope i cleared things up a little. thanks for all your info. you guys are way over my small brain it wll take me 6 month's if ever to digest it all [thanks lots]
Festus

Hot Core and Lawn Dart,
Could you please explain to me how one can use pressure data from a lab to calibrate a strain gage system used at home. I understand that you intend to use identical loads and compare their results to yours. But unless you send your barrel to them along with the ammo, how can you dtermine how much signal difference is due to instrumentation, and how much is due to actual pressure changes between their barrel and yours?

Gents,
A common question, and an impossible one to answer for the amateur individual, I've been wrestling with this one myself. Like festus's conclusion, I try and stay within loading manual limits, but as I play with oddball calibers and some old rifles with modern powders for which there is no data, it is flying by the seat of one's pants. Start low, be cautious, and refine my reloading consistency and techniques. I rarely go anywhere near max loads, seeking accuracy instead.
Hats off to you lawndart, you're clearly way ahead of the curve. My current practice is to realise that I can only operate with me, my firearms and techniques. To seek 'absolute' values that are applicable across the board is not my problem, lol. So many variables in the reloading process that I'm happy if I can find what works for me.
Cheers,
R*2

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Originally posted by Idaho Shooter:
Hot Core and Lawn Dart,
Could you please explain to me how one can use pressure data from a lab to calibrate a strain gage system used at home. I understand that you intend to use identical loads and compare their results to yours. But unless you send your barrel to them along with the ammo, how can you dtermine how much signal difference is due to instrumentation, and how much is due to actual pressure changes between their barrel and yours?

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Good question. Not as great as "If 300 hunters in Idaho each shoot a wolf with a 220 Swift, 300 with a 25-06 and 300 with a 300 Win Mag, what do you get? (answer: more elk), but still very good.

A certified lab follows (or should) the relatively strict SAAMI criteria which specify chamber and bore dimensions, temperature and humidity, distance to the chronograph, specifications for the conformal piezo-electric transducer, etc., etc. Send samples from the same lot of ammunition to different certified labs and the data that each lab reports should be PDC (Pretty Damn Close). What the home experimenter wants to know is "What would the lab report the pressure and velocity for my ammo to be?" The data that the home experimenter gets from his Pressure Trace or Oehler system will likely indicate a lower pressure than what the certified lab would report. That difference will be fairly consistent across a range of powder charges. By telling your software what it "should" have gotten for a given pressure reading, it will then be able to apply that correction factor across the board.

There are two over-riding factors to keep in mind when discussing determination of "pressure" of ammunition.
1. There is no way to directly measure pressure. All methods, be they CUP via tarage tables, Piezo-electric transducers or strain gauge technology, calculate pressure by indirect means.
2. Good lab technique is more important than having a range full of fancy equipment.

lawndart

Hey Idaho Shooter, JCN hit it dead in the " X - ring" with his response to you.

That is the thing that has been missing in all the Threads discussing(and generally degrading to arguing) the HSGS devices. As you can clearly see, JCN understands a whole lot more about what is actually going in the HSGS than anyone else on this Board that I've ever tried to corner into the correct answer. But, none of them ever figured it out.

Anyone with a HSGS that has not gone through the JCN HSGS Calibration Method, might have Low, Correct or High Pressure Indications. Just no way to know until the HSGS is "properly" Calibrated so it becomes a useful SGS.

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"If 300 hunters in Idaho each shoot a wolf with a 220 Swift, 300 with a 25-06 and 300 with a 300 Win Mag, what do you get? (answer: more elk).

Thanks again JCN. Haven't seen that and it is so true.

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From Festus:
what im trying to do is find lowest preasure with the highest velocity witch some manuals show me. but what than is the highest preasure i should stay away from in all load's listed for that cal.

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Hey Festus, My original recommendation of looking in the Hodgdon and Speer Manuals will provide exactly what you want. Since you "apparently" do not have them, I can recommend them highly.

Hodgdon #26 is great and still in a "Book" style. And Speer #12 or #13(as well as some previous ones) also provide the SAAMI MAX, but they do not show individual Pressures like Hodgdon. You might find a deal on them at eBay or another auction site.

By the way, Hodgdon still has a FREE handout Manual you can get at your local Gun Shop that sells Reloading Supplies. Or you can request one directly from them.

These question's i have stem from a 30/30AI iam loading for. not much out there for loading info on this cal. I have the ak manual's but some say he developed these loads in a mauser. dont know but he has some very high velocity's. what i was trying to find out is if i stay under 40'000 psi in this 30/30 336 i should be in the ball park (or not).
Festus

Hey Festus, You should have mentioned 30-30 AI in the beginning. Look for the Thread by "Deke" on "Pressure Ring Expansion". Then get his email address and establish some communication with him. He has been working with a 30-30 AI for a year now.

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Just no way to know until the HSGS is "properly" Calibrated so it becomes a useful SGS.

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Unless, of course, you follow the National Institutes of Standards and Technology instructions, the links to which have been posted here many times. Hot Core doesn't seem to think NIST knows what they are talking about. What would they know? They only set the standards for the whole country.

quote:

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Originally posted by Hot Core:
Hey Festus, You should have mentioned 30-30 AI in the beginning. Look for the Thread by "Deke" on "Pressure Ring Expansion". Then get his email address and establish some communication with him. He has been working with a 30-30 AI for a year now.

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I'm sorry Hot Core, but Pressure Ring Expansion (PRE) is totally worthless as method for evaluating cartridge pressure. There are several very mature, and accurate methodologies for inferring cartridge pressure including lead crushers (shotgun), copper crushers (centerfire handguns and rifles), direct piezo-electric transduction, conformal piezo-electric transduction, and strain gauge methods. Those all work. Unfortunately they all require time, money and careful lab technique.
PRE is attractive to the home reloader because it is cheap, easy, and doesn't require an investment in training and time. Unfortunately it just doesn't work.
There just is no shortcut, or easy way to discover the actual pressures of cartridges.


lawndart

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From JCN:I'm sorry Hot Core, but Pressure Ring Expansion (PRE) is totally worthless as method for evaluating cartridge pressure.

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Hey JCN, We will just have to disagree on this issue. I've used both PRE and CHE for right at five decades and find them very useful "Pressure Indicators". And both PRE/CHE have been in use by knowledgeable Reloaders for well over 100 years.

It hasn't been all that long ago(well maybe it has been) that the good folks at Speer used CHE as a Recommended Pressure Indicator in their Manuals.

That does not mean I disagree with you about PRE/CHE being unable to tell a person what the actual Pressure is, that is not their purpose.

Still agree with you that the other methods are far better when properly Calibrated using the JCN Method. But, as you mention few people will go to the expense to do it properly.

Best of luck to you.

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That does not mean I disagree with you about PRE/CHE being unable to tell a person what the actual Pressure is, that is not their purpose.

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Oh? So PRE/CHE aren't calibrated after all? They are just a relative system, as both Ken Waters and I have said all along?

Lawndart,
Okay, I see the how calibrating your strain gauge system and your firearm with the SAAMI labs would be useful to a manufacturer of custom reloaded ammo. This would be a good way to ensure that your ammo does not exceed SAAMI industrial specs, and is as safe as that from a major manufacturer in customers' weapons. But as I understand your answer it still gives you no way to actually calibrate your rifle, as the nature of firearms makes it impossible to achieve a standard for comparison.
Instead it seems to me that you are stanardizing the ammunituon.
Do you have any way to determine if your rifle is giving pressure 10,000 PSI above or below the average of the SAAMI labs.
The reason I am asking is that we have all heard of the rifle which gives excess pressure signs with published reloads or with factory ammo.
In the case of factory ammo, we already know that is is within SAAMI spec. I do not see how sending the ammo to a lab will tell you what it is doing in your rifle.
At the risk of being redundant, I understand that it will tell you how your ammo compares to factory ammo, but not how your rifle compares to SAAMI barrels.
Is there enough uniformity from one stain gauge system to another, that you can compare your signal data to the labs, and make a valid judgement as to the actual pressure curve in your firearm?

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Is there enough uniformity from one stain gauge system to another, that you can compare your signal data to the labs, and make a valid judgement as to the actual pressure curve in your firearm?

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Let me chime in with a simple answer to your question: Yes.

There is a standard NIST procedure for calibrating an unknown system without having an artifact with a known quantity of the units you're trying to calibrate in. As another poster stated, practically all systems are indirectly calibrated in this way. A simple example is the speedometer in your car. You cannot get an NIST traceable standard for miles per hour. You can get a standard for distance, and you can get a standard for time, and it is up to you to put the two together, speed = distance/time. When you do that, you know speed as well as you know distance and time.

The exact same procedure applies to strain gage firearms systems, per NIST, the US government's experts on the subject. The expression is more complex than distance/time. The last two unknown quantities that you have to plug in are the ID and OD of the chamber at the point where the strain gage is affixed. Once you have that, the strain gage system is as calibrated as a speedometer calibrated by a known distance vs. time.

PSI readings taken on one rifle are directly comparable to PSI readings taken on another rifle. This does not say that the same cartridge produces the same pressure in different rifles. It does say that whatever pressure is generated in both rifles is known, and in the same, useful units, and are therefore directly comparable (ratio data, to be exact). One great advantage of this is that you know the peak PSI for a cartridge and your rifle, not the PSI that the cartridge produced in a different test rifle.

All this has been discussed on this board many times, and I have posted links to the NIST site, where they tell how to do this. Last time I did that, CDH posted a beautiful example of a PSI calibration he regularly does at work, following the NIST procedure. It's not firearm related, but it does yield a PSI calibration good to .02%, without reference to a PSI standard (which isn't available anyway).

The one and only unit of measure that is still calibrated by reference to an artifact in the same units is mass. ALL OTHER CALIBRATIONS ARE FROM DERIVED UNITS.

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From Idaho Shooter:Is there enough uniformity from one stain gauge system to another, that you can compare your signal data to the labs, and make a valid judgement as to the actual pressure curve in your firearm?

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Hey Idaho Shooter, That is the main thing you get from the JCN HSGS Calibration Method, it allows you to adjust whatever the readings are from a HSGS (actually too low, correct, or too high) by a comparison with what the real "Standard" happens to be as established by SAAMI.

EXAMPLE: Let's say a person has a HSGS and goes through the set-up sequence the very best they can. They don't have access to a way to accurately measure the Chamber Wall Thickness and do the best guess they can.

Now they go buy a box of Factory Ammo and test 10 of them in their rifle with the Strain Gauge attached somewhere on the chamber. Lets say the HSGS tells them it measures 65,000psi.

Now they take the other 10 cartridges and send them to a Certified SAAMI Approved Lab and they test them. They determine the Factory Ammo is measuring 55,000psi.

Lets also say the SAAMI MAX PSI for that cartridge is 60,000psi.

Then the Certified Lab sends you the info and you look it over. You know your HSGS is reading 10,000psi too high, but it is still 5,000psi below a SAFE SAAMI MAX for that cartridge.

Now you can go out and use your HSGS as a Calibrated SGS and know (even though it is not recording what it should) you can SAFELY load to 70,000psi according to your SGS and it will really be close to the actual 60,000psi that it should read.

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In the same way, your HSGS "might" initially record 60,000psi, the Caertified Lab determines the same ammo is also 60,000psi and you can believe your HSGS is actually(as amazing as it may be) providing accurate psi data.

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Same if the ammo reads high on the HSGS, but Low at the Lab. You just adjust the data for the variance.

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The biggest mistake is becoming convinced that a HSGS is accurate "without" first doing the JCN HSGS Calibration Method. Maybe it is accurate, but the Laws of Probability are against that.

quote:

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Originally posted by Tailgunner:
Clark
I think your reading somthing into my comment that wasn't intended.

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Sorry.

I could handle the biz trips, 24 hour shifts, head cold, and eye infection.
But when my comp crapped out, and I had to surf the internet from work, I got grumpy.


Clark

Hot Core
You stated "Now they take the other 10 cartridges and send them to a Certified SAAMI Approved Lab and they test them. They determine the Factory Ammo is measuring 55,000psi.

Lets also say the SAAMI MAX PSI for that cartridge is 60,000psi.

Then the Certified Lab sends you the info and you look it over. You know your HSGS is reading 10,000psi too high, but it is still 5,000psi below a SAFE SAAMI MAX for that cartridge.

Now you can go out and use your HSGS as a Calibrated SGS and know (even though it is not recording what it should) you can SAFELY load to 70,000psi according to your SGS and it will really be close to the actual 60,000psi that it should read."

This necessitates the assumption that there is no pressure difference between your firearm and the SAAMI spec test barrel. We know this will seldom be true.
If for some reason your weapon is producing inordinate high pressures (such as a rough bore or an eroded throat), your procedure will have invalidated the data which might tell you so.
Consider this scenario: I have loaded my 30-06 with 165 gr BT's over 60 gr of H4831. I send the ammo to a SAAMI lab and they tell me the ammo is producing 50,000 psi. I know that my mod 70 is good for at least 70,000 psi. Well I might as well boost my load 10 or 15 kpsi.
But perhaps this rifle has been rebarreled with an extremely tight bore. My HSGS says it is producing 65,000 with the original load, so according to your instructions I subtract 15,000 psi to "standardize" it with the SAAMI lab's results. Now I can increase the charge weight, or go with a faster powder,(because I can not squeeze 66 gr of H4831 into the case) until my HSGS tells me I have reached 80,000 psi, minus a correction of 15,000 equals 65,000 target.
This sounds to me like a good way to get hurt and destroy rifles.

Denton,
Thanks for the information regarding NIST. I have not been following these discussions long enough to have seen these previous posts.
As I gain familiarity with the new format of this forum, I will search the archives and find these links.

The short version of the NIST material is this: If you have an unknown, that you can write an equation for in terms of input variables that you know, then the unknown becomes known to accuracy as good as you have for the input variables.

There are two ways to get the equation. One is from known equations, such as speed = distance/time. The other way is to find the equation through experimentation.

The strain gage system works from the first method. The only key variables that change from rifle to rifle are the ID and OD of the chamber at the point where the gage is attached. You do have to also include the thickness of the brass casing at that point, but it's a fairly minor influence.

The net is, if you follow the instructions, and can do three measurements to reasonable precision (plus or minus .1-.2% or so), all the other terms in the equation are known, and every time you pop off a shot, the computer solves the equation and gives you real PSI. It's really calibrated, per NIST.

Thought experiment: How do the labs calibrate their piezo equipment? They do it indirectly, using the NIST procedure, same as calibrating a strain gage system. They have no source of 60 KPSI standards to compare with, same as the rest of us.

BTW, at least one publisher of loading data uses a strain gage system.

Denton,
One CAN learn something new each day.
My only experience with strain gauges has ben in weight measurement systems. And of course in a scale one calibrates the unit spanning it at zero and with a known mass. It does not matter how well the strain gauges are standardized as the computer calibrates the scale using this span.
I was unaware that strain gauges could be used without comparison to a known artifact.
We only need two signifcant digits of accuracy from a pressure measurement system in order to keep us safe as reloaders. After searching some of your earlier posts I see that the strain gauge system is capable of an order of magnitude greater accuracy than that.

quote:

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From Idaho Shooter: If for some reason your weapon is producing inordinate high pressures (such as a rough bore or an eroded throat), your procedure will have invalidated the data which might tell you so.
Consider this scenario: I have loaded my 30-06 with 165 gr BT's over 60 gr of H4831. I send the ammo to a SAAMI lab and they tell me the ammo is producing 50,000 psi. I know that my mod 70 is good for at least 70,000 psi. Well I might as well boost my load 10 or 15 kpsi.
But perhaps this rifle has been rebarreled with an extremely tight bore. My HSGS says it is producing 65,000 with the original load, so according to your instructions I subtract 15,000 psi to "standardize" it with the SAAMI lab's results. Now I can increase the charge weight, or go with a faster powder,(because I can not squeeze 66 gr of H4831 into the case) until my HSGS tells me I have reached 80,000 psi, minus a correction of 15,000 equals 65,000 target.
This sounds to me like a good way to get hurt and destroy rifles.

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I certainly understand what you are getting at. Things like Bore Condition are totally ignored by some of the posts you will see on this subject. Normally when a person brings up "all the variables" they are then deluged with posts they resort to nothing but name calling, because they have nothing of fact or substance to offer.

I do agree that is a valid concern in an older barrel. The part which I did not include (and I usually do at some point in these posts) is that the Reloader still needs to use ALL Pressure Detection and Pressure Indications available to them as they develop the load from below.

That way, your concern would still be addressed, irregardless of the indicated psi on a HSGS.

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If we consider the barrel and chamber being tested has no strange Pressure Rising quirks, then the above explaination is valid. The info received from SAAMI would adjust your HSGS to the same Pressure that Factory Ammo has as it's SAFE MAX.

So, going by your rough barrel example, it would be UNSAFE to fire Factory Ammo in your erroded barrel.

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One of the most totally illogical comments you will find in the archived posts is that some folks actually believe you can Calibrate a HSGS by repetitive firings with cartridges of an unknown Pressure value.

If you believe that makes good sense, there is no need for you to read any of my posts, and best of luck to you. If on the other hand you see the foolishness of such trash, I'll be glad to help you in any way I can.

quote:

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One of the most totally illogical comments you will find in the archived posts is that some folks actually believe you can Calibrate a HSGS by repetitive firings with cartridges of an unknown Pressure value.

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Another Hot Core fabrication--a new one for the list! I have followed these threads very carefully, and nobody has ever made that assertion. Now somebody did say that you could calibrate the PRE method by comparing with factory ammo, which is pretty much an unknown pressure. And that somebody was.... Hot Core.

He has just called his own comment totally illogical, and has transferred it to the system he opposes.

Hot Core, how do you expect anyone to take you seriously, when you keep making stuff up like this? A phony EE, claims that the PRE method is calibrated, followed by statements that it is only a relative system, statements that dial caliper measurements of chamber dimensions are just a guess, the PRE method is completely repeatable, and on, and on, and on.

I stand corrected. This is not a new fabrication. It is an old fabrication, being recycled.

quote:

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Originally posted by Hot Core:

I do agree that is a valid concern in an older barrel.

...

If we consider the barrel and chamber being tested has no strange Pressure Rising quirks, then the above explaination is valid. The info received from SAAMI would adjust your HSGS to the same Pressure that Factory Ammo has as it's SAFE MAX.

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And what makes "strange Pressure Rising quirks" exclusively endemic to "older barrels" (whatever your undefined threshold for "older" may happen to be)? A tight, new bore is perfectly capable of causing higher pressures with the same ammunition than is recorded in a SAAMI test barrel. Likewise, an improperly chambered or throated new barrel will also cause different pressures than from the same ammo fired in a SAAMI test barrel. The only way your "calibration" works is if your barrel is equivalent to a SAAMI test barrel. Without going through extensive and exact measurements, you don't know that. You are assuming critical values are equivalent between your rifle and the SAAMI test configuration. In fact, your "calibration" may very well be leading you toward dangerously high loads, as Idaho Shooter correctly noted -- his specific example of an old, eroded bore in no way means that the general problem of inequivalencies between your rifle and the SAAMI test configuration is restricted to old barrels. In fact, in order to prove via extensive and exact measurements that your rifle is, indeed, equivalent to a SAAMI test rifle, you would introduce greater errors than would denton or NIST in measuring ID and OD.

Your strain gage "calibration" method is inadequate, incorrect, and inferior to the methods denton has advocated.

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From InfoSponge:And what makes "strange Pressure Rising quirks" exclusively endemic to "older barrels" (whatever your undefined threshold for "older" may happen to be)? A tight, new bore is perfectly capable of causing higher pressures with the same ammunition than is recorded in a SAAMI test barrel. Likewise, an improperly chambered or throated new barrel will also cause different pressures than from the same ammo fired in a SAAMI test barrel.

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In his quest to begin an argument Info Sponge apprently either overlooked the obvious or misunderstood what is happening with the excellent JCN HSGS Calibration Method. It simply allows a HSGS user to be able to "actually get accurate Pressure Data" as verified by a Certified SAAMI Lab. Nothing else available will allow the user that information.

With the Calibration Information, the previously misleading and totally worthless HSGS can become a useful SGS. And the SGS user still has the option to Develop Loads at any Pressure Level he desires. If he finds he is getting Pressure Indications when the SGS indicates a Low Pressure, then it is still obvious that "Increasing Loads" should be STOPPED until the source of the Pressure Increase is determined.

If anyone out there does not understand that concept, then you really need to avoid wasting your money on a HSGS.

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Originally posted by Hot Core:

If he finds he is getting Pressure Indications when the SGS indicates a Low Pressure, then it is still obvious that "Increasing Loads" should be STOPPED until the source of the Pressure Increase is determined.

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Obviously. Equally obviously, the fact that a strain gage system that is properly calibrated according to your methodology is still capable of producing actual pressures far different from the recalibrated readings from the strain gage is a clear indication that your "calibration" is nothing of the sort.

Knowing what pressure a given load produces in a SAAMI test barrel doesn't help you know with any precision what pressure that load will develop in any other barrel unless you already know what pressures that other barrel will produce relative to a SAAMI test barrel. Without having gone through extensive measurements, calculations, and testing, you don't know that, and as a result, you can't use your methodology to calibrate a strain gage attached to your barrel unless that barrel itself has previously been calibrated against a SAAMI test barrel. You have given no means of assessing the equivalence of your barrel to a SAAMI test barrel, nor any analysis of the errors present in making that assessment. That means your "calibration" procedure is useless in determining accurate and precise pressures from a strain gage attached to a barrel of unknown relationship to a SAAMI test barrel. That is why you are forced to rely upon traditional "pressure indicators" even after you have supposedly calibrated the strain gage pressure measurement system.

On the other hand, denton's procedure of using measured ID and OD values in the hoop strain equation provides strain gage pressure readings with a known error magnitude that is entirely adequate for safe reloading -- and without the need for a known relationship in reference to a SAAMI test barrel.

Please address the technical issues without engaging in ad hominem arguments.

A long time ago, we experimentally determined that Info is quite well acquainted with Msrs. Halliday and Resnick. He is technically competent.

There are serious problems with Hot Core's proposed calibration method, just as Info has said.

One is that you have no good basis for calculating the bias to correct for a SAAMI cut chamber vs. an average chamber. It is in the 2-3,000 PSI ballpark, but it's still a fairly rough number.

The far more serious problem is that it is only a point estimate. For the same number of observations, you can check the whole curve (line in this case), which is far more useful, if you're inclined to do such a thing.

Checking at least five points on the whole curve follows the NIST procedure for when you don't have a good theoretical model. It is technically feasible, but not economically practical, or necessary, since we have a good theoretical model.

No cartridge has a peak pressure independent of the rifle it is fired in. One great advantage of the strain gage system is that it gives you the pressure of the cartridge you made, with your jar of powder, in your rifle, not the pressure of some other cartridge, made with a different lot of powder, fired in a different rifle. That fact alone improves accuracy more than enough to swamp out any inaccuracy from dimensions that are .001" off, or a slight error in the Poisson ratio for steel.

Has anyone else noticed that Hot Core's objections to the repeatability of the strain gage method have suddenly evaporated with his new focus? Suddenly, that's not a problem anymore, if you just compare pressures at one point.