chambered221 wrote:

... The most important thing to keep in mind is that all 3 have independent properties. Because of this there are no formulas to convert one to the other. Conversions have been tried and there are similarities but nothing that can be dependable and safe when dealing with max pressures.

As said, there is NO conversion even though there is some correlation. You know how I like to tinker with numbers and I went round and round with this some time back. The PEAK pressure is the important number, safety wise, and the only really accurate measure of that is from the electronic equipment. CUP and LUP are only INDICATORS of the pressure. I know that Speer has reshot some of their loads to get accurate PSI measurements to replace the CUP measured loads they used previously.

I could see this getting into an intersting discussion. Our ears work on sensing pressure to translate sound for us. When addressing hearing safety, peak pressure as well as duration are the key factors in determing the affects and resultant hearing damage. Same with noise damage to the lungs (I work with escape systems and explosives in cockpits). A noise or pressure pulse that has a high peak pressure but short duration is often safer than a lower peak pressure that is longer in duraction. That could be why when you are looking at maximum load data, the maximum pressures listed have some variation.

Correlation is very different from conversion.
There is one very important reason that you can't convert from CUP to PSI:
The Copper Crusher pellet has to be under a minimum amount of pressure before it begins to crush. (it has a "dead zone"" It is also only sensitive to pressure over a period of time. (it takes a certain amout of time for pressure to move the metal)
The problem with converesions is that the strain gauges don't have any "dead zones". It measures direct chamber pressures throughout the entire pressure range - as exactly as the system used can.
A high pressure fast burning powder will have little time over the start pressure of the copper crusher and the time the pressure drops below where it will measure pressure at all. This means that you get a LOWER maximum pressure reading with the crusher for that load than you would with a powder that produces the same pressure over a longer period of time. The PSI strain gauge will sample the pressure levels many times during the combustion process and show the pressures at each interval. It will plainly show that the peak pressures are the same as well as the rise time and the complete pressure curve of the complete event.
Is there a correlation? YES! both are corrolated to the chamber pressure.
Is there a usefull formula that can be used to load to current PSI units from the CUP measurements? NO! because many of the old loads tested showed that they were over-pressure loads with higher peak pressures than SAAMI standards were meant to allow.
We have been using this data for years - it has always worked in that time, how far off base can it be? The lack of catastrophic failures is more a matter of good guns than it is a matter of reasonable load data. Many guns, when carefully examined have shown micro-fractures due to a long history of loads that exceeded the standards associated with SAAMI spects. Lesser guns will have failed long ago. Those who are more conservative in their loading techniques have guns whose chambers sho no signs of micro-fractures. The newer load data is safer in our guns - and some loads have been reduced to reflect the changes. The SAAMI specs for safe pressure loads show that CUP data has been superceded by the PSI data. Unfortunately some manufacturers have no desire to retest old and obsolete data to reflect the difference in loads. Those that have are the reloaders best friends. Guns will probably continue to be made stronger than they need to be but with computer engineered models being more common there is a real and present danger that some newer guns could fail when using some of the loads listed in the old manuals.
One example of this is the data using H110 / WW296 in 357 magnums. Some guns (Smith and Wesson and others) failed using the old data. It has been lowered to accommodate the lighter revolvers because the manufacturers show that their pistols should be able to take the listed pressures. The new PSI has actually increased to reflect the actual maximum pressures while the loads have been reduced. Some of the old loads were actually more than 30% over the maximum SAAMI standard and no one knew it.

One thing I quickly learned from reading Rinkers book.
The terminology and definitions used in the ballistics world don't always go as one would think.

He goes through great length to make sure the reader understands what definitions are applied to what terms.

I believe we got some of that going on here !!!

Thanks to Paul for picking up on one of them !!!

Thanks Paul for some great insight!

I did try some H100V in the 25-06, along with a few other powders. I was loading Nosler 100 Accubonds.
Unfortunately, my rifle didn't group as well with H100V as it did with another powder, so I didn't pursue H100V loads- and I didn't chronograph any H100V loads.
A few observations: There is quite a bit of airspace in a 25-06 case with H100V.
H100V is actually an extruded powder- with a very big BUT- the grains are about the size of grains of salt! H100V meters like a ball powder.
Judging from the low loading density in the 25-06, I suspect H100V might be a great powder in some smaller cases, like the 243, 257 Roberts, and the short mags.