Tut, I've now located a second opinion--similar to the first one I listed (12,000 psi proof). Baron Engelhardt's article in the 1961 Gun Digest Treasury says that for 16ga or larger, the standard proof for smokeless--which is the single star over PSF--is 12,800 psi. That's still not much over the SAAMI service pressure for 12ga loads of 11,500 psi, and I'd either stick to CIP loads or low pressure reloads.