Home Forums Hunting & Shooting Handguns 45 LC "heavy" loads in a S&W Model 25?

I actually never derived a formula for pistols.

The whole project started when I wanted to figure out the PSI limit for my milsurp Swede. As I looked at the rifle data, and as I tested it statistically, it had some curvature to it. But the curvature was slight, and a straight line was a very good approximation if you limited pressures to between 30 KPSI and 65 KPSI. That answered my burning question, and that is all the farther I took it. So I published my finding with those pressure limits.

My comments caused quite an uproar, since many people were convinced of the correctness of SAAMI's incorrect statement that PSI and CUP were not correlated, and that one could not be calculated from the other. So it was with some pleasure that I discovered that Dr. Brownell had reached my conclusion a few decades earlier. It was especially nice that he used equipment I had worked on at Tektronix, and that he was trained by the same people who trained me. (Dang, I feel old!)

Here are his graphs. He is using the term "Correlation Factor" incorrectly, but you'll get the right idea looking at his work.

Basically, he confirms what you've probably heard before: At low pressure, CUP=PSI. As pressure increases, CUP systematically underestimates PSI.