Can anyone tell me the formula to convert CUP to PSI and versvisa?
Also, what is the safe PSI for a modern bolt action chambered in 9.3 x 62 (CZ 550 Am)? Some loading manuals show PSI from 38,000 to 48,000. Are these pressures and loads kept lower cuz of the older actions or is this about right for PSI in this cal?

There is no direct formula.

for the range of pressure of roughly 40,000 PSI to 70,000 PSI one can estimate by the formula
PSI=(1.516)CUP-17902

Give credit to Denton for this math..... I find it works fairly good.

RE: the CZ bolt rifle. If it's chambered for the .270 Winchester which runs about 61,000 PSI then it should also run the 9.3 X 62 at that PSI as well.....Finding the load data that shows that pressure might be a bit difficult but someone here has experience and will help out.

I might add that Stubble is correct in saying there is no direct conversion but this one does a good job of approximation.

Aiiiieeee! Cheeewowah! Here we go again!!

quote:

Originally posted by stubblejumper:
There is no direct formula.

THERE IS NO DIRECT CORRELATION, AS IT VARIES FROM ONE CARTRIDGE, BULLET, POWDER TYPE & LOAD TO THE NEXT. For example, in the .45/70 with bullets from 350 to 500 grains, CUP and PSI are pretty much the same identical number!!

quote:

Originally posted by steve4102:
Also, what is the safe PSI for a modern bolt action chambered in 9.3 x 62 (CZ 550 Am)?

Any modern bolt action will stand pressures FAR BEYOND what the brass cartridge case can stand. It is the brass case that is the weak link in the system, and brass will limit what is feasible regardless of the action!

Having two measurement systems, that measure the same thing, and that are both reasonably successful, and which are not correlated and convertible to each other is a mathematical impossibility.

http://www.shootingsoftware.com/tech.htm

Take the time to read the article.

There are a couple of likely explanations as to why SAAMI introduced the error that the two systems are not correlated.

1. They were trying to straighten out the mess the world was in, because for decades, we thought that the CUP system produced readings in actual PSI, and the terms CUP and PSI had been incorrectly used interchangeably. Someone without a lot of mathematical background meant to say that PSI and CUP are not the same thing, and misspoke, saying they were not correlated or convertible.

2. They did try regression, to see if they were correlated, but made the rookie mistake of using a set of identical cartridges, and measuring them with both the CUP and PSI systems. That never works, because the "span" on your input variable is zero, and all you end up seeing is the random error in both systems.

CIP, the European equivalent of SAAMI, is completely untroubled by the issue. They publish both CUP and PSI (also MPascal) data. The strong evidence is that they abandoned actually taking CUP data, and use a formula to generate CUP from PSI (MPascal) data. If it works on that side of the pond, it has to work here.