Bill & Stan get it - it depends on the powder and components.
The other point I was hoping to make is that:
1. load pressures have changed little from the smokeless powder loads of the mid-1890s, for which the U.S. makers proved their barrels in-house
2. the oft' said "Those old guns weren't designed for the pressures of loads today" is wrong. Esp. small bores, some pressures are documented to have been higher.
Smokeless Powder Co.'s “S.S.” (Smokeless Shot-gun) was a 43 grain = 3 Dram Eq. that was discontinued because small bore pressures were markedly higher.
