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kenny Rookie Member


Joined: Dec 22, 2007 Posts: 5 Location: Tucson Az.
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sagebrushsniper Member


Joined: Feb 22, 2008 Posts: 31 Location: central wyoming
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Posted: Wed Apr 02, 2008 8:43 pm Post subject: Re: CUP-PSI |
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Copper Units Of Pressure. They use a special pressure barrel and insert a specific cupper crush unit and go from there. The use has been reduced with the use of computerised "stretch" of pressure sensitve units. Someone correct me if I'm wrong.
_________________ Payback is hell with no due date. If it aint' important enough to wait to do till tommorow it ain't important! |
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Vince Site Admin


Joined: May 25, 2005 Posts: 15929 Location: Brisbane AUSTRALIA
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Posted: Wed Apr 02, 2008 9:57 pm Post subject: Re: CUP-PSI |
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Gidday Kenny. I have often wondered the same thing. I sorta understood the crushing of the copper pellets and the measuring of PSI....but I didn't know how they related to one another....soooo, I thought damn it...Mr Google knows everything, I'll ask him. Below is a link to many of his answers. You will find the answer to your question in there.
I would answer it for you (now that I know  ), but I think that it will make more sense if you read it for yourself from a number of different sources like I did.
Google Search on CUP vs PSI
Cheers, Vince
_________________ Cheers, Vince 
Illegitimi non carborundum
(Never let the bastards grind you down)
Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God.
"Nulla Si Fa Senza Volonta."
(Without Commitment, Nothing Gets Done) |
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Pumpkinslinger Super Member


Joined: Sep 22, 2007 Posts: 5052 Location: NC foothills
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Posted: Wed Apr 02, 2008 9:59 pm Post subject: Re: CUP-PSI |
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Sagebrushsniper, you're right. "Copper Units of Pressure" is determined by crushing copper slugs. PSI (Pounds per Square Inch) is an actual measure of the pressure, done by using strain gauges. There is no straight conversion factor between the two.
_________________ Mike
"I ain't no better than anybody else, and there ain't nobody better than me!" Ma Kettle |
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FALPhil Super Member


Joined: Aug 18, 2007 Posts: 377 Location: Dixie
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Posted: Thu Apr 03, 2008 4:36 am Post subject: Re: CUP-PSI |
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Keep in mind that you cannot translate between the two. C.U.P. is an absolute measurement based on a batch of identical copper pellets and no two batches are alike. Therefore, 50,000 c.u.p. does not equal 50,000 psi. Heck, 50,000 cup from one batch of pellets doesn't even equal 50,000 cup from another batch of pellets.
_________________ The Wicked Witch of the West is alive and well and serving as the Speaker of the House. |
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kenny Rookie Member


Joined: Dec 22, 2007 Posts: 5 Location: Tucson Az.
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MGKelly Rookie Member


Joined: Feb 06, 2008 Posts: 24 Location: G. R. Michigan
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Posted: Fri Apr 04, 2008 5:42 am Post subject: Re: CUP-PSI |
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Very interesting thread, I always knew that CUP and PSI were not the same. Whats interesting is the amount of difference between the two, and indiscriminate interchanging of either could land you in dangerous territory. As it has been said the CUP measurement between two "identical" cartridges can differ, but it was the only way of figuring out chamber pressures before the advent of electronics. Personally I think maybe the CUP system of measurement should be abandoned and PSI used exclusively, if only to eliminate the "confusion factor". Would I be wrong to say that the CUP system is essentially obsolete now that there are far more accurate methods and insturmentation?
M. G.
_________________ Doing the "right" thing for the wrong reason is still wrong.
PETA: People for the Eating of Tasty Animals
Euthanasia: Viet Nam
Euthanmideast: Iraq |
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Vince Site Admin


Joined: May 25, 2005 Posts: 15929 Location: Brisbane AUSTRALIA
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Posted: Fri Apr 04, 2008 6:01 am Post subject: Re: CUP-PSI |
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MGKelly wrote: |
Would I be wrong to say that the CUP system is essentially obsolete now that there are far more accurate methods and insturmentation? |
I think you may well be right MG. However, there will always be those that are more comfortable with the old unit of measurement....like me with Imperial/Metric measurements.
I learnt Imperial then had to change over to Metric, although I still convert cm and metres to inches and feet an kilometres into miles because they mean something to me.
Cheers, Vince
_________________ Cheers, Vince 
Illegitimi non carborundum
(Never let the bastards grind you down)
Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God.
"Nulla Si Fa Senza Volonta."
(Without Commitment, Nothing Gets Done) |
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FALPhil Super Member


Joined: Aug 18, 2007 Posts: 377 Location: Dixie
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Posted: Fri Apr 04, 2008 8:12 am Post subject: Re: CUP-PSI |
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Vince wrote: |
MGKelly wrote: |
Would I be wrong to say that the CUP system is essentially obsolete now that there are far more accurate methods and insturmentation? |
I think you may well be right MG. However, there will always be those that are more comfortable with the old unit of measurement....like me with Imperial/Metric measurements. |
Now that piezo-electric strain gages have gotten dirt cheap, I don't see why CUP should stay around. CIP in Europe uses strain gages, but publishes in different units.
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sagebrushsniper Member


Joined: Feb 22, 2008 Posts: 31 Location: central wyoming
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Posted: Fri Apr 04, 2008 9:04 am Post subject: Re: CUP-PSI |
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Just ask a subject of the given bullet if it hid to hard and if so back off a couple of grains! Ha never had a dog complain my 60 gr. .243 were going to slow, just were to accurate to dodge! Also brass last longer if not stretched at max pressure!
_________________ Payback is hell with no due date. If it aint' important enough to wait to do till tommorow it ain't important! |
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Pumpkinslinger Super Member


Joined: Sep 22, 2007 Posts: 5052 Location: NC foothills
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Posted: Fri Apr 04, 2008 6:16 pm Post subject: Re: CUP-PSI |
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From what I'm reading in the loading manuals PSI is replacing CUP as time permits and for any new loads.
_________________ Mike
"I ain't no better than anybody else, and there ain't nobody better than me!" Ma Kettle |
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twofifty Member


Joined: Feb 07, 2007 Posts: 158 Location: BC Rockies
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Posted: Sat Apr 05, 2008 11:27 am Post subject: Re: CUP-PSI |
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Pumpkinslinger wrote: |
From what I'm reading in the loading manuals PSI is replacing CUP as time permits and for any new loads. |
Thank god CUP isn't replaced by, get a hold of this mouthfull of metrication pap: 'kilopascals'.
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Pumpkinslinger Super Member


Joined: Sep 22, 2007 Posts: 5052 Location: NC foothills
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Posted: Sat Apr 05, 2008 2:12 pm Post subject: Re: CUP-PSI |
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Well, when you boil it all down its just a number for comparison purposes. I don't think many of us have a way to measure peak pressure (sure wish I did!) and there is no way to calculate it.
_________________ Mike
"I ain't no better than anybody else, and there ain't nobody better than me!" Ma Kettle |
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WASAJCO Rookie Member


Joined: Mar 19, 2008 Posts: 6
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Posted: Sat Apr 05, 2008 5:20 pm Post subject: Re: CUP-PSI |
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Pumpkinslinger wrote: |
Well, when you boil it all down its just a number for comparison purposes. I don't think many of us have a way to measure peak pressure (sure wish I did!) and there is no way to calculate it. |
 Oehler says different:
Oehler Personal Ballistic Laboratory
Not cheap, but good things never are.
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1895ss Super Member


Joined: Jul 21, 2005 Posts: 2612 Location: Not Here...!!
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