Modern shotgun shells usually consist of a plastic case, with the base covered by a thin brass-plated steel cover. As noted above, paper peels used to be common, and are still manufactured, as are solid brass shells. Share the publication How plastic cartridges are made. A shotgun cartridge can accomplish anything from lightly splashing a clay target at close range to knocking down a deer at 35 yards.
And that huge variation in capacity can result from the commercial side of a single gun. This is because you can precisely adapt what is inside a case to your specific needs.