1. Thoughts regarding
chamber lengthening are here
http://www.lcsmith.org/faq/chambers.html 2. Thoughts regarding
forcing cone lengthening are about 1/3 down here
http://docs.google.com/document/d/1ZIo0y746UsSRZIgRuuxwAbZjSBHitO_EanvwLYc-kGA/edit and
http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=459320#Post459320 http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=400793#Post400793Short version
1. I would never lengthen the chamber of a British or Continental double.
2. I would be VERY hesitant to lengthen the chamber of a U.S. maker vintage 16g and especially 20g double.
3. Vintage U.S. maker
12g doubles were, for the most part, manufactured with stout barrels. I have measured the wall thickness of lots of 12g doubles and BY AN EXPERT BARREL SMITH, most chambers can be lengthened.
4. Lengthening the forcing cone is of almost no concern in U.S. vintage doubles. The exterior taper of the barrels is less acute than the angle of the cone, so
every one that I have personally measured has wall thickness in the forcing cone equal, or greater than, the wall thickness at the end of the chamber.
16g L.C. Smith victim of an inexpert attempt at chamber lengthening
