Math isn't my greatest subject either so, someone check these figures.
In the other thread 1biggun asked about bolt thrust at 42,000 cup on a .308 and 50,000 cup on a 7.62x39. I found a formula to convert cup to psi. Now this will only be a ballpark figure as there are +/- in both cup and psi. So hitting either end of the +/- could give different results. The formula is Cup x 1.516 -17902 = PSI. So, taking your .308 at 42,000 cup should be around 45,770 psi. The 7.62 at 50,000 cup should be around 57,898 psi. Now we need to figure the square inch we have touching the bolt head. The .308 is .473 inch across so, the radius is .2365. We take .2365x.2365x3.14=.175 square inch of area (I think). The 7.62 is .444 inch across so the radius is .222. So .222x.222x3.14= .154 square inch of area. Now we can take the psi x the area to find the amount of pressure on the bolt. For the .308 at 42,000cup/45,7700psi the force on the bolt is 8009 pounds. The 7.62 at 50,000/57,898psi the force is 8916 pounds. If we bumped the .308 up to 60,000 psi the force is 10,500 pounds. Now none of these figures take in to account the friction between the brass case and steel camber. These are just pressure figures at a certain pressure on a certain area.