Ejector marks vary with brass hardness and not all brands of brass are created equal. My point being you could get ejector marks with one brand and none on another brand.
Military Lake City and commercial made brass for the military has the hardest brass in the base followed by Lapua.
In another forum a long range competitive shooter tested his Lapua brass below until he had brass flow into the ejector. He then backed off the load several grains knowing the elastic limits of the brass. As you can see in the chart below if he had tested Remington or softer cases he would have gotten ejector marks much sooner at a lower pressure. Another method is to measure base expansion just above the extractor groove.
How Hard is Your Brass? 5.56 and .223 Rem Base Hardness Tests
http://bulletin.accurateshooter.com...r-brass-5-56-and-223-rem-base-hardness-tests/
Simple Trick for Monitoring Pressure of Your Rifle Reloads
http://www.hodgdonreloading.com/rel...-trick-monitoring-pressure-your-rifle-reloads
I'm cheap and buy bulk once fired Lake City 5.56 and 7.62 brass knowing the brass is made Ford Truck Tough.
Not only is the Lake City brass harder, the flash hole web is also thicker giving the base more radial strength. And this makes the primer pockets last longer before becoming oversized.