Re: Any sign to be alarmed? Headspace separation?
Larry is correct. Your case photo shows only the normal rub of an FL sizing die.
The "bright ring" that is the incepient indicator of a head seperaton occurs after firing, not after sizing.
None of that means you AREN'T getting excessive case stretching, only that what your photo shows isn't of that type.
Most, if not all, head seperations are the result of repeated excess shoulder set back when FL sizing, not high pressure or excess rifle headspace, as such.