I believe you're right about the 70,000 psi on wildcats, but we don't need to pressure-test any of the factory loads. The SAAMI maximum average pressure for the 7mm Weatherby and 7mm STW is 65,000 psi, just as it is for the 7mm SAUM, 7mm WSM and 7mm RUM. So the velocities they're getting, whether with factory ammo or SAAMI-member handloading data (such as Nosler's) have been pressure-tested at not more than 65,000 psi.
All we really need is for some 7mm Mashburn enthusiast to loan their rifle and handloads to somebody with a Pressure Trace or other strain-gauge setup, and we can find out what the pressures are.
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