Again, the published length of the factory load is not nearly as important as the pressure it generates to begin with. Much is made over a factory shell being 1/4" longer than the chamber length of older short-chambered doubleguns, but most of them aren't 2 3/4" in length when fired, anyway. Pick up some different brands of fired hulls next time you're at a range. Take them home and measure them. I've never found but one or two loads that opened to a full 2 3/4 inches.
I recently measured several different brands of fired hulls that are sold as 2 3/4", again. None measured that. Most were closer to 2 5/8".
