--- doesn't it stand to reason that barrel bursts could occur under those same conditions? Why? Do you suspect the barrels were weak? Frames crack from backthrust and barrels from hoop stress.

What do paper hulls have to do with cracked frames or burst barrels?

Hull length is increasingly important as pressure approaches the gun's design limit. Low pressure 2 3/4" loads should have no issue in a 2 1/2" or 2 9/16" chamber. Equally, it would be no trick to load high pressure loads in a 2 1/2" hull that would be quite injurious to most 2 1/2" chambered guns; they might be called proof loads.