To continue with Drew's historical references:

Some of the nation's top trapshooters intentionally used longer hulls in shorter chambers. Those old paper hulls, opening just into the forcing cone, provided some cushioning for the shot in the pre-plastic wad days. They got better patterns. A.P. Curtis, who worked in the US firearms business for over 40 years, wrote a 2-part series in the American Rifleman back in the 30's, touting the BENEFIT of slightly longer hulls in producing better patterns. (Note that those benefits no longer exist--assuming you're using plastic wads, which provide even better cushioning for the shot.)