Soaking in oil , penetrating oil but only guarantee it to be killed till dry .how do you kill a primer? I'd read that soaking in oil would work.
If you can , meaning noise , you can fire the primer in an EMPTY case . As long as there's no powder and bullet it'll give near identical results . To be sure , have 5-10 sized or new cases , prime and fire . Take the average .
Usually a I phone or iPad will enhance the photo of the fired enough to compare to fired cartridges .