The ammunition companies in the late 19th and early 20th centuries sold primed paper case shells in volume, but not so much to individual shooters. Different parts of the country supported local shotshell loading companies who specialized in making loads which were very popular in that specific area, for example Duck and Goose loads in areas having lots of duck or goose hunting activity. Such companies would buy the primed paper cases, then load them with purchased powder, wads, and shot using their own equipment to meet seasonal demand. That practice had pretty well died out by the time of WWI, as the big factories had expanded their load offerings so that they covered almost any possible market demand. Some of the ammo companies' catalogs of the time listed hundreds of different loads. From a 1914 Peters distributor's catalog: