It is important to recognize that shells loaded to CIP standards (English, Italian, etc.) have two service and proof pressures:
“Standard Proof” lead or steel, limited to no larger than 3.25 mm / U.S. No. 4 and max. fps 1,300.
Maximum Average (Service) Pressure 740 BAR = 10,733 psi;
Maximum Statistical Individual Pressure 850 BAR = 12,328 psi;
Mean PROOF Pressure 930 BAR = 13,489 psi

“High performance/Superior Proof”
Maximum Average (Service) Pressure 1050 BAR = 15,229 psi;
Maximum statistical individual pressure 1200 BAR = 17,405 psi;
Magnum proof 1320 BAR = 19,145 psi

If the shells are "Superior Proof" the box will be so marked.

Smith guns were not designed for service pressures of > 15,000 psi