I mentioned earlier that .22 rimfires have ground glass in the primer and that they rely on the crimp to build up pressure. Or they did, 30 or 40 years ago, when I learned those things.
Wondering if they still use the glass, and what the current thinking is on crimping rimfire cartridges, I came across this informative piece from _American Rifleman_:
Maybe this will add to your store of knowledge. The story on crimping centerfires is full of arguments and opinions, but this is the clearest piece I've seen on rimfires.