totaldla said:
If you can still get the Western powder download, it has both 55k saami and 62.3k nato load data.
There is an interesting example of how even the professionals have been tripped up by 5.56/223 pressure differences. Those Western loads produce 13% higher pressure than the standard 223 Rem MAP because someone at Western believed the SAAMI conformal transducer system would match the readings produced by the CIP transducer system. They don't. I called Western about this in about 2017, IIRC. The ballistic tech I spoke with confirmed they had used a SAAMI-type conformal transducer and SAAMI reference loads to calibrate in producing those pressures. If they wanted to match what the CIP measures as a maximum load, they needed to use a CIP reference load's CIP-rated pressure to calibrate.
The difference is neatly illustrated by the U.S. military. The first image is for M193, and you can see they list the exact same pressure difference between the copper crusher and transducer that SAAMI does, so you know their measuring systems tracked the ratio of the two measurement types the same as the SAAMI systems do. That's important because when you get to M855, which is our military's interoperability ballistic twin to the European SS109, you see the 55,000 PSI by copper crusher rating goes to 58,700 PSI by transducer, and not to the 62,366 PSI number used by the CIP. Only the European measuring systems would read it that high.
So Western took a pressure that should have been 58,700 PSI on their conformal transducer, or about 7% over standard 223 Rem SAAMI MAP, and instead gave us 13% over SAAMI MAP, and which would read somewhere around 66,260 psi in a CIP measurement. Oops!
But here's what is useful about that mistake. Given the difference between a SAAMI test barrel chamber and the NATO test barrel chamber produces about a 2,000-3,000 PSI difference, even plopping a round of M855 into a SAAMI test chamber barrel will not reach the pressure Western loaded to for that list. And if, after a decade, Western hasn't had reports of gun problems with those loads that caused them to issue warnings and withdraw the list, then guess what? The guns handle those pressures. They are, after all, still below the SAAMI proof pressure range (73,500 to 78,500 psi). Just be aware they will accelerate throat erosion, the same as anything making higher temperatures and pressure will do. I don't recommend them for that reason, but it is interesting to see how they been hanging around.