In talking conversion, most folks tend to think of cartridge pressures in terms of "pounds per square inch" or "bars per square centimeter". So if a rifle now accepts a cartridge rated at 52,000 psi, it should have no problem with another cartridge rated at the same pressure level, even though the second cartridge has a larger diameter, right?

Well, no. When going from a smaller cartridge to a larger one, don't forget those square somethings. A cartridge with a .30-'06 base size has an internal base size of around 1/10 square inch. So a cartridge with 52k psi pushes against the bolt face with around 5200+ pounds. But as the cartridge base increases, the internal base size increases as well. What is 1/10 sq. in. in a .30-'06 could be about double that as the internal base area increases and the pressure against the bolt face could double, even though the "per square inch" internal pressure is the same, 52k psi.

Jim