I do have a large variety of headstamps of .223 brass to try out. After a rather scary batch of badly loaded .223 rounds, I now have an LE Wilson Case Gauge and that has made a huge difference in keeping my loaded ammo consistent. I can also cross-reference the case gauge with my own barrel as well when I get the chance.
I can try the sharpie test with a snap cap, so that there's no chance of a primer going pop in my presence.