Here's one that's ready to give up just forward of the cannelure after 4 firings in an M1A (7.62mm LC89Match). I had the sizing die set such that the shoulders were being set back by 0.008" instead of the usual 0.004'ish. I had two full blown separations in this batch along with a bunch of others that had partials. The more subtle ones just had a little bit of a wrinkle.
If you're FL resizing without using a case gage to set the die, you stand a good chance of seeing these firsthand. Using the manufacturer's directions on how to set the die is just a half step better than guessing.