Thank you for that very cogent explanation. It is very helpful. My point was only that a gunmaker, for commercial reasons, might not necessarily request the highest proof, even though the gun in question might be able to satisfy the higher proof test. Incidentally, how does one ascertain what the pressure of one's ammo is? Is all standard 2-3/4 inch US ammo roughly the same? Does it make any difference if it is Rio, Winchester, Fiocchi or Estate (I.e., foreign or US manufacturers or licensees)? Is the SAAMI standard a maximum? P. S. When you feel up to it, I wouldn't mind a short course on other countries' proof houses. Interesting stuff I think. Thank you.