The constriction of the choke in these guns was tighter because they were made during the time shotshells only used fiber wads and didn't have shot protectors. "Choke" refers to the percentage of the shot load impacting within a circle of a given diameter at a given distance. The amount of constriction necessary to do this varies with the improvements in shotshell manufacture as well as shot size. Therefore, less constriction is likely necessary with modern shells, for the same level of choke.
Mike
