Pressure for Dummies?

[S.B.]

I understand PSI but what is CUPS and what do I have to do to convert from PSI to CUPS? Also, why is there more than one way to measure pressure in cartridges? One better than other?
Steve

[Cowpox]

I'm not sure about CUPS, but a number of years ago, we had CUP and LUP.  CUP was copper units of pressure, and of course, LUP was Lead units of pressure.

The pressure gun had a recess where a small pellet of copper or lead was placed, and the expanding gasses forced a ram against the pellet of metal.

Chamber pressure was then computed from the measured amount of deformation on the pellet.

[Cowpox]

Update,  CUP means White Labratories did the measurement, and CUPS means SAMMI did it.

[BBF]

Last I read was that there is no mathematical conversion available betwen CUP and psi.

[S.B.]

Is there a difference between pressure measured in CUPS and CUP?
Steve

[trotterlg]

There have been lots of attempts to compare CUP to PSI and no one has ever been able to come up with a formula to make it work.  They are different methods of measuring pressure, and seem to vary with each other depending on so many different factors as to make the direct conversion from one to the other impossiable.  Larry

[no guns here]

There was an article in the past month or two in one of the mags, I "THINK" it was Shooting Times.  Basically, the CUP is a one-event measurement device.  It only measure the highest pressure event that happens during a shot.  The conformal transducer can measure and records the entire pressure event from it's beginning until it's end.  No real correlation between the two.  I'll try to remember to look up the article tonight and post a link.


NGH

[no guns here]

Found it!   Read: http://www.shootingtimes.com/ammunition/ST_cuppsireloaddata_200905/index.html

Thanks,
NGH

[S.B.]

Anyway, back to the question, Is there a difference between pressure measured in CUPS and CUP?
Steve

[no guns here]

I understand PSI but what is CUPS and what do I have to do to convert from PSI to CUPS? Also, why is there more than one way to measure pressure in cartridges? One better than other?
Steve

The original question had nothing to do with "Is there a difference between pressure measured in CUPS and CUP?"

The original question asked how to convert from PSI to CUP, secondarily it asked is there more than one way to measure pressure.  The second question asked which was the better way to measure pressure.

We've tried to answer the questions you posed.  I posted a link that led to a much more authoritative source than most of us here could give.  Sorry for trying to answer your question.  If you wanted to know the difference between CUP and CUPS, you should have asked.


NGH

[S.B.]

Is there a difference between pressure measured in CUPS and CUP?
Steve

Cowpox stated:Update,  CUP means White Labratories did the measurement, and CUPS means SAMMI did it.
The reason for my second question.
Steve

[EsoxLucius]

There is not a direct conversion between CUP and PSI.  However, there is a formula which shows they are highly correlated which can be used for estimation purposes.  Obviously the formula works best for cartridges closest to the trend line.  Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portative or CIP, the European equivalent of SAAMI, routinely uses a similar formula.

http://www.shootingsoftware.com/ftp/psicuparticle2.pdf

Copper crusher data produced by SAAMI and White Laboratories should be very close as the methodolgy and equipment used by both are similar.