Note also the Fryxell/Lee formula is intended to determine the psi at which "obturation" begins. It does not determine the psi of any "load". Fryxell was also referencing bullets in revolvers needing to obturate to seal the cylinder throats. The formula does not reference calculation of a loads psi.....hence my questioning the relevance.
BTW; the formula says my 30 XCB cast of #2 alloy (WQd) with a BHN OF 22 should obturate at 31,680 psi.....yet at 2900 fps pushed at a measured psi of 49-50,000 psi recovered bullets and excellent accuracy show no sign of obturation.......or alloy failure.