Many people habitually shoot low pressure loads in short chambered guns put up in longer hulls. They don't blow up their guns, nor do they end up in the hospital.
Its the "LOAD" that's much more important than the exact length of the hull. No shell should be fired which is long enough the "Loaded" shell is forced into the forcing cone as this can retard the opening of the crimp creating a pressure spike in the chamber.
Both Gunmakers & Proof Houses have sanctioned the use of shells with a loaded length shorter than the chamber, but which will upon firing when the crimp opens the end of the hull will lap into the forcing cone a bit.
Most factory 2 3/4" shells are loaded to a higher pressure level than should be used in the shorter chambered guns. It is however the load, not the length, which eliminates their use.
