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[shoot back]

Could someone explain in simple terms how to figure psi on different loads when it is written as cup? Is there a simple way to convert one to the other?

[jwalts27]

Severel other forums have pissing matches over this info. on occasion.


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

and this.

Copper units of pressure or CUP, and the related lead units of pressure or LUP, are terms applied to pressure measurements used in the field of internal ballistics for the estimation of chamber pressures in firearms. These terms were adopted by convention to indicate that the pressure values were measured by copper crusher and lead crusher gauges respectively. In recent years, they have been replaced by the adoption of more modern piezoelectric pressure gauges that more accurately measure chamber pressures and generally give significantly higher pressure values. This nomenclature was adopted to avoid confusion and the potentially dangerous interchange of pressure values and standards made by different types of pressure gauges. Pressure is a fundamental thermodynamic parameter that is expressed in units of force divided by area. In the avoirdupois system, the units of pressure are pounds per square inch and in the metric system, the units or pressure are newtons per square meter (pascals). A chamber pressure measured with a copper crusher gauge would be expressed as psi (CUP) in the English system or MPa (CUP) in the metric system

Courtesy of Wikipedia

[Engineer1911]

No, there is not a conversion factor. PSI is measured with a strain gauge and "electonic stuff" at the moment of firing. CUPS are measured by the amount of "crush" on a copper plug mounted in a pressure barrel. PSI is an instantaneous value of peak chamber pressure. CUP is a value calulated after the cartridge is fired in a pressure barrel.

You are comparing automatic transmission fluid to gear lube. The only thing in common is "quart". A cooking recipe calls for 2 cups of flour, but you buy flour by the 5# pound bag. You can make a conversion if you know the density of flour and a calculator.

The chamber pressure theorists have killed gazillions of electrons discussing this very subject. Down at our level of 'Reloading Science', we just shouldn't worry about it.

Pick the starting load and make ammo. One grain equals 0.0023 ounce. This is close enough. Read your reloading manual load data and the introductory stuff in the front that "explains" Pressure Measurement.

This is an attempt to keep things simple, just like the book "Everything Men Understand About Women", without being rude or insulting you. Some things can't be done, just accept it.

[venomballistics]

there is a relatively easy way.
first, invest in a universal receiver and test barrels.
next you fire a string taking measurements with the CUP method.
then you fire a string using the piezo transducer method.
Now you may compare results for this particular load under test.
Incidentally any conversion ratio determined will only apply to that specific load.
Conversions will need to be done for each specific load.
or you could just forgo the copper crusher method and just use the piezo method.

either way ... you'll find far more value and satisfaction in a Porsche 911 at a similar cost

[Engineer1911]

There, we minimized the deaths of stray electrons and successfully brought closure. Now what about bear loads?

[scooter123]

A simple solution is to download the 1993 SAAMI/ANSI Specification. In there you will find the maximum pressure in both CUP and PSI. BTW, somewhere between Handgun and Rifle Pressures there is a flipflop in which is higher, because IIRC the 357 Magnum is 44,000 CUP/35,000 PSI and 308 W is 52,000 CUP/60,000 PSI. So, don't use any of those conversion equations you can find on the Net, IMO they are not reliable in every caliber.

[ArchAngelCD]

Originally Posted by scooter123

A simple solution is to download the 1993 SAAMI/ANSI Specification. In there you will find the maximum pressure in both CUP and PSI. BTW, somewhere between Handgun and Rifle Pressures there is a flipflop in which is higher, because IIRC the 357 Magnum is 44,000 CUP/35,000 PSI and 308 W is 52,000 CUP/60,000 PSI. So, don't use any of those conversion equations you can find on the Net, IMO they are not reliable in every caliber.

There ya go. Then stick with published data that won't generate more pressure than it should and you will be safe.

Welcome to the forum!