Bruce (at BRP) suggested that I also measure the case at the mouth of fire formed brass and I got 0.357" on every case that I checked (at least 25+).
That would be the inside diameter of the fired case neck, not the outside. Remove any vestige of the old crimp before measureing. Take a caliper and place it in the fired case mouth. You should be able to turn it without grabbing, but it will scrape at the point you take the reading.