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I wouldn’t be using any lubricant that might compromise the detonation from the primer.

I use a K&M hand primer (from Workshop Innovation), that gives good adjustability for primer seating depth....

Lapua SRP primer pockets are about .003 deeper than standard (0.122 versus 0.125). You must be crushing your primer anvils a fair bit, normally would set them 0.002-0.006 below case head.