Ok, so in relation to my other thread on caliber/cartridge design and max pressure...

What is it that determines if a given firearm action/design can handle the pressure of a given load?

I have a feeling it is a combination of both operating pressure of the round and the amount of surface area that pressure is exerted over.

Is this the case?  Or something else?  Mebbe explain it to me?


Take the TC Contender as an example - 223 is fine.  Some could say it is a classic Contender chambering.  62k in pressure per saami spec.  

But you know what you don't see? 762x39 Contender barrels.  Or manufacturers willing to make them.  Apparently the action isn't quite strong enough to really handle the load on a regular basis.

But the saami spec for 762x39 is a hair under 52k psi.

The only difference, as far as I can tell, is the amount of surface area the case head presses back against, and the actual diameter of the case and the material removed from the barrel blank to make the chamber, etc.

30-30 Winchester is another popular Contender chambering.  Larger  case head area and case body volume than the 762x39, but max psi is "only" 42k.

Yep, you have identified what determines the amount of stress placed placed on the action.  Then the strength of the action by the materials used, the yield strength of those materials and the design of the action and the stresses ( hoop, shear, etc.) that design incurs from the pressure the particular cartridge creates.

Example:  the Weatherby Mark V action is probably the strongest commercially available small arms bolt action ever made.  Theoretically, it can withstand 200,000 psi.

Very simple. Bolt thrust! https://en.wikipedia.org/wiki/Bolt_thrust

That same contender can shoot 45/70 loads which has a much larger case head than even 7.62x39, But your limited to the pressures you can run with 45/70. Pressure will increase bolt thrust at a far greater rate than case head diameter.

Action type, material usage, hoop strength, lug engagement, all play a role in the yield strength or max pressure the firearm can withstand.

Yep.  The Mark V action is insanely strong.

In regards to single shots the Ruger No. 1 action is considered the strongest.  I remember reading something a while back where Ruger engineers were actively trying to blow one up and could not get the action to blow up even with obscenely high pressures.