I'm not Erich, but think I read the same stuff he does. Here it is:
writer Sherman Bell in his 4+ year, 9-part “Finding out for Myself” series in The Double Gun Journal. Sherman Bell wrote on topics such as: Shooting longer shotgun shells in shorter chambers: 2 ¾” in 2 ½” or 2 5/8” chambers. Bell shoots all sorts of modern loads in antique guns while monitoring pressure with a pizeo-electric device. The results: Pressure difference is minimal at best, often averaging less than 1,000psi difference.
I would advocate reading the article and the caveats before attempting such a practise, a few exceptions do apply. For a careful, thoughtful shooter who has done their research, it's not as dangerous as many think. I personally use short shells in short chambers.
