I found an online calculator for CUP. If anyone's got a load that they have physically tested and KNOW for certain the CUP value.......would you please humor me and run the numbers through this program?? Very interested to see how valid the numbers come out. Thanks in advance!!

http://solidrocktechnologies.com/bin/cup.cgi?muzzleVelo...nownR=&knownW=&known

I think that might be a Denton website. This is sure to drag Hot Core out of hybernation!

Denton is way too smart to use the Powley calculations, or CUP, for that matter.

See the fine print at the bottom of the page. "The CUP Formula used is the Powley formula, from "Handloading" by William C. Davis, Jr."

I don`t think you`ll get any bites on a load with a measured CUP value from a handloader that doesn`t have access to a ballistics lab. The equipment needed to develope a CUP figure isn`t available, to my knowlage, to the hobby reloader as a strain gage system is.

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I think that might be a Denton website. This is sure to drag Hot Core out of hybernation!

Nope, Denton works with a strain system and deals in PSI not CUP, although he has tried to find a relationship between the two. He can`t give a measured CUP value for a load.

Hot Core as you say likely will chime in though. Denton or not.......

As I recall the Davis work is based on the equations from Powley. There is supposed to be a mistake in it (Ken Howell) but I don't know what it is. The coulpe of times I used it, it seemed to take a lot of time. The results were believeable.
Good Luck!

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Originally posted by popenmann:
Denton is way too smart ...

Hey Strut10, Obviously popenman did that for "my" amusement. Anyone wanting to see how brilliant denton happens to be can take a look right here at The World’s Most Ignorant Reloading Suggestion. That says everything " I "(or anyone else) need(s) to know about denton's knowledge.

As for the CUP info, I feel sure I have some old Powder Manufacturers Manuals around here with various Loads and the respective CUP info in them. I can try to find some of them if you are interested.

Is there a specific cartridge or cartridges you are interested in?

/

Without knowing the Expansion Ratio, W and F2 and using Method 3 the result for the Marlin 1895 300 grain bullet maximum load with H4198 from Hodgdon #27 is 30,818 CUP. Hodgdon pressure tested that load at 40,000 CUP. Perhaps the calculator would be closer with a known expansion ratio, W and F2. I thought with the Powley calculator one also specified the flavor of IMR powder used as well.

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Originally posted by Hot Core:
The World’s Most Ignorant Reloading Suggestion.

That method of depriming is not unusual. Ross Seyfried published an article about depriming Berdan cases with a homemade one-legged punch similar to the so-called "World's Most Ignorant Reloading Suggestion". Apparently Ross is one of the world's most ignorant reloaders, too? Didn't the Lee Loader use a similar method of depriming? Don't benchrest shooters and shuetzen shooters who reload at the range sometimes use a similar "knock-out" method of depriming?

I miss Denton's contributions to this forum.

Nothing ignorant about knocking primers out with a punch. What's ignorant is not knowing that primers have so little power that good eye protection and a stout leather glove are all the safety equipment needed to do so.

Back on topic, I ran across what purported to be a mathematical formula to convert psi to CUP. I did not like the fellow's assumptions nor his habit of throwing out examples that did not match his formula, but anyone interested enough to dig around can find it by googling PSI CUP correlation.

Now you dunnit dj and popenmann... Don't throw logic into the HC/Denton pissing matches!

Why would anyone use or care about CUP anymore? It's difficult, clumsy, archaic, erratic, and only slightly more precise than case head measurements.

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Why would anyone use or care about CUP anymore?

While I totally agree with this, there is still some value in being able to (roughly) equate CUP to PSI when one finds loading data that is expressed in CUP as is still the case with a lot of data from the Alliant (and other) data. It'd be my wish that all ammo data be expressed in PSI or as I understand a new international measurement the CIP.

BTW, can someone explain the CIP and is it convertable to PSI?

Ken Oehler published a conversion from CUP to PSI in the '90s (see his current column in RIFLE SHOOTER).

PSI to CUP conversions is actually one area where I still disagree with Denton. FWIW, Dutch.

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Originally posted by CDH:
Why would anyone use or care about CUP anymore? It's difficult, clumsy, archaic, erratic, and only slightly more precise than case head measurements.

'Cause there is still a ton of CUP data out there, some of it still listed as psi, and 'cause I started loading so long ago that I still think in CUP.

There is no exact conversion between CUP and psi. Many variables determine the error, and no simple conversion will be exact. The snide remark about it being as reliable as case head expansion is just plain goofy. One reason it is still used is it's simple, cheap, and reasonably accurate. Further, it takes some effort to develop a psi rating for a cartridge, and many of the old cartridges don't sell enough to make it worthwhile; the old CUP ratings will likely remain forever for those. I'm not certain, but I suspect new cartridges standardized by SAAMI don't even have a crusher (CUP) rating at all, just the piezo.

Regarding the CIP (SAAMI's counterpart in Europe), they have crusher and piezo numbers just like SAAMI, but the crusher arrangement isn't the very same one, so they can get different numbers. Denton has demonstrated that the piezo (psi) ratings at CIP are determined by a very simple conversion formula from the original crusher (CUP) rating! So take that, ye who doubt the conversions.

I've summarized what I've read over the years in this page.

On that page you'll find a link to a Powley Computer, one which is more complete than the one linked above. The equations Powley offered break down at the "edges". The reliability of the estimates vary with both pressure, (relative) case size, and bullet SD. On the whole, it does a decent job (if you keep its limitations in mind).

Lastly, Strut10, just get a copy of Hodgdon's Annual. There's plenty of CUP data there you can plug into these CUP estimators and see for yourself how they work. Lyman 48 has similar data as does the older A-Square manual.

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Originally posted by popenmann:
...That method of depriming is not unusual. Ross Seyfried published an article about depriming Berdan cases with a homemade one-legged punch similar to the so-called "World's Most Ignorant Reloading Suggestion". Apparently Ross is one of the world's most ignorant reloaders, too? Didn't the Lee Loader use a similar method of depriming? Don't benchrest shooters and shuetzen shooters who reload at the range sometimes use a similar "knock-out" method of depriming?

I miss Denton's contributions to this forum.

No, not when it is a LIVE Primer!

I miss denton too, not many gave me as many laughs due to complete Reloading ignorance.

Must admit if you, popenman, don't understand why it is dangerous to pound on a LIVE Primer with a "Sharpened tool" that you might do right well as a denton surrogate.

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I miss Denton's contributions to this forum.

I had assumed I just hadn't noticed any of his posts recently. I now find he hasn't posted here in almost a year. What happened? Did he move on to another forum? I too enjoyed his comments.

edit: I see he's still active over at 24hourCampfire, so he must have tired of the sometimes, ah, "rough" behavior here.

IMO Denton got tired of the constand tirades and outright attacks from our resident pressure expert HOTCORE. I couldn't blame him for leaving...it was pretty bad.

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The snide remark about it being as reliable as case head expansion is just plain goofy.

No, it's a jab at HOTCORE, high priest of case head measurement for pressure evaluation. It's not our first...

Ref: PSI vs. CUP

I understand the desire to understand...but if the old data is published and believed safe why do you care if it is in CUP or PSI? Are you trying to replicate the data? Use CUP to test new loads? Figure a PSI from old CUP data to test new loads? The last I can see as worthwile I guess...

As to the applicability of converting CUP to PSI (SAMMI) to PSI (CIP), well CIP measures at the case mouth, SAMMI measures at (essentially inside) the cartridge body. Technically they are measuring at different points and the numbers will never match exactly.

CUP to SAMMI PSI is different, both are measuring #1 the exact same pressure event and the #2 exact same point. Those are VERY important points!

Denton said it best, but I'll paraphrase...if two different measurement systems are measuring the same thing, they are able to be converted back and forth. Think about that for a moment...it assumes that both are good, repeatable measurement systems of course.

AS long as they measure the same event, they are convertable...fundamental physics in action. A=C, B=C, therefore A=B

The problem is that the differences in the methods do skew the numbers. CUP has a very large experimental error (*), something like 8k PSI or more in some cartridges, where piezo measurements are generally on the order of 1k PSI or less. A simple analysis (statistics, ugh) whereupon you graph the pressures for various cartridges (the more the better) with CUP on the left axis and PSI on the right (for example) will show a clear relationship/trend. IIRC mathmatically plotting the relationship gave a conversion good to something like 10-15% error. The relationship is there. It is up to you to determine is the relationship is accurate enough for your purposes...I'm not the one behind the trigger!


(*) IMO the CUP error is the result of the copper cylinder continuing to deform during other than peak periods of the pressure curve...giving a somewhat 'averaged' pressure value, not just peak pressure. Piezo plots the whole curve, allowing the actual peak to be easily determined...

Since you asked a question, I'll give you my answer. I plugged in a hot 7x57 load with a 140 grain at 3000 fps that shows 62000psi on a strain gage. With this CUP estimator, it comes up to 48900 CUP which coincidentally is not too far off from most conversions from CUP to psi.

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Originally posted by CDH:
IMO Denton got tired of the constand tirades and outright attacks from our resident pressure expert HOTCORE. I couldn't blame him for leaving...it was pretty bad.

I do agree with that synopsis.

The only thing I'd add is that I tend to give out what I receive. I have no problem at all disagreeing with folks - in a civil way.

CDH's and popenman's hero simply waded into the deep end of the pool and got in way over his head, way over his first-hand experience level and WAY OVER his general ballistics knowledge level.

If he couldn't take receiving, what he handed out, then perhaps he did the best thing he could do for himself.

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The snide remark about it being as reliable as case head expansion is just plain goofy.

Of course it is - goofy!

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No, it's a jab at HOTCORE, high priest of case head measurement for pressure evaluation. It's not our first... ...

Smile when you say that Pilgrim!

I'd even skipped right over it. Couldn't figure out where asdf got that bit of total "goofy" ignorance about CHE.

Then I saw it was from CDH and I must admit it brought a BIG old smile to my face.
---

Anyone with even a modicum of relevant Reloading Experience realizes CHE is a great tool and that PRE is even better. So, considering the source of the "jab", it was funny to me - believe it or not.

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(*) IMO the CUP error is the result of the copper cylinder continuing to deform during other than peak periods of the pressure curve...giving a somewhat 'averaged' pressure value, not just peak pressure. Piezo plots the whole curve, allowing the actual peak to be easily determined...

I don't see that as an error. CUP is measuring the ability to move brass, which is what I want measured. I don't give a damn about transient peak pressures which are too brief to move brass.

btw, in a sealed volume, gas pressure is gonna be the same no matter where you measure it.

leftoverdj; This reminds me of the argument that CUP measures the effects of pressure on metal which is realy what we are concerned with.
Good Luck!

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btw, in a sealed volume, gas pressure is gonna be the same no matter where you measure it

I disagree in principle. This is not a sealed volume we're working with! The bullet is moving down the barrel, causing a constantly changing volume. The gas will be moving at a high enough velocity and is swinging though a high enough range of pressures that measuring the pressure on one side of a restriction (case shoulder) will be different. THe principle of pressure drop through a restriction is widely used to measure gas (and liquid eccasionally) flow...think orifice plate if you have any industrial experience.

Is it a significant difference? Probably not for our purposes...SAMMI PSI and CIP PSI are not too terribly far apart in the cartridges rated by both. It's certainly well within the range of safety when using modern arms.

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Then I saw it was from CDH and I must admit it brought a BIG old smile to my face. Big Grin

Glad I could be of service...laughter is good for the heart!

HSGS RULE!

The chamber is not a sealed container, and the
"gas" is quite heavy , hot and moving rapidly.
This means that the Ideal gas laws are modified quite a bit. Think of the cylinder gap in a revolver and how little really escapes from the highly columnated gas stream.
Taint Simple

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Originally posted by CDH:
...HSGS RULE!

Gee, HC, when are you going to convince Doc Oehler, or your buddy HOWL, or Denton, or Saeed, or any other of the idiot experts that they don't know shit from shine-ola about all the faults with the strain gages. And that they all should be better off if they used only PRE and or CHE instead of using any and all pressure signs that may be available, including chrono'd bullet speed. best-o-luck