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What does CUP abbreviation mean?
The Dutchman
Member Posts: 811 ✭✭✭✭
Seen it many times...could not find a definition. What does CUP mean in reloading manuals?
Comments
quote:Originally posted by ladams
Copper Unit Of Pressure. It just an alternative to using PSI for pressure. PSI and CUP do NOT interchange, so never assume that a load with 51,000 CUP is the same as a load with 51,000 PSI. There is no way to convert the two.
Correlation can be a word that some folks stumble across without having a distinct definition pertaining to a particular application. Attempts to correlate CUP/LUP/PSI bring this problem of a nebulous definition to the forefront. The relationship between them is tenuous at best.
This is a short article that has been floated around the internet for a while taking on the idea of correlation:
http://www.shootingsoftware.com/ftp/psicuparticle2.pdf
Best.
There are lies, damm lies and statistics.
Figures don't lie, but liers can figure.
Think of Correlation as "equal in some ways, but not all ways" For instance take two triangles that are the same shape. All three angles are equal. Even though the the sides are not equal in length, they have equal ratios to the other triangles sides. In this case each triangle correlates to the other.
To apply this to our problem, CUP was an approximation of pounds per square inch because of all the soft metals it would crush most consistently. But it was still called CUP, not PSI. People(and some engineers, scientists and technicians) started interchanging the two. No can do. You must know how to Convert one to the other. also note in the article that CUP has a much larger random error probability.
So, along comes the technology that can accurately measure super high pressures. And we find it has drifted off what we thought was a straight across conversion. but the ratios are still the same as pressure increases. Barring the variablity of the random error the author spoke of. In this way CUP and PSI are correlated, just not equal. You would have to know how to convert one to the other to use that data safely. Or, you can follow the manual and learn how to check and read pressure signs yourself.
I neither stated nor implied 'exact' simply because the term doesn't have application in this instance.
"noun: a statistical relation between two or more variables such that systematic changes in the value of one variable are accompanied by systematic changes in the other "
It is the concept of the relationship between the changes that is most important here.
I've swapped e-mails with the author and I think he's put a lot work into developing his own understanding of the relationship between these two or three variables. However, there are drawbacks to this theory within the entirety of the concept. It is not universally applicable across the board. It's a good start but not the end all of explanations.
My opinion is that this is a non-essential pursuit because we don't need both and the Americans have finally succumbed to using a system of assessing pressure that is useful and meaningful. There is no reason to have a method of conversion between CUP and PSI, get rid of one and start using the other. If the data doesn't exist for PSI for some cartridges, start developing some.
Best.