Rustystud
Threads area strange animal. You would think that a finer thread would not be as strong, but the added area of more threads plays into this.
As soon asI get a chance, I will slip the assy back into the jack and take it up in slight increments untill it fails.
As far as actual tonnage on the thread when a case fires, it is a ridiculous small amount when compared to the strength of even the 16 tpi over the 18tpi.. I sectioned a 308 case at the head, and it measures close to .400 on that inside diameter at the web. Using your pressure formula of bolt thrust, (in psi), divided by 2000, you come up with:
.4 divided by 2 = .200, square this and you get .04, multiply this by 3.14 and you get .1256, (area of inside of case), x 60,000 psi gives you about 7600 psi at the bolt face, divided by 2000, gives you about 3.8 tons.
Now, I doubt the actual barrel sees much more, but suffice to say that a thread that will hold 25+ tons of pressure is in no danger of failing under anything that a case can produce.
I suspect the bolt lugs will fail before the threads would be blown out the front.........jackie