Having tried every primer pocket and flash hole uniforming thing on this planet, I quit after getting equally accurate results with no prepping whatsoever. Several barrels in .308 Win. and 30 caliber magnums all shot 3/4 moa at 1000 or better.
Most often forgotten thing that causes primers to not function too well is a weak firing pin spring. Especially if your firing pin protrusion from the bolt face is less than .055 inch. I'd replace bolt gun firing pin springs every 3 years; 2's better. Doesn't matter how many rounds are fired. When your load starts having elevation spreads way too big, the firing pin's weaker rating is often the culprit.
Primers detonate the biggest and most uniform when they're smacked almost hard enough to drive 'em out the case mouth and all the way out the barrel.
Replace your current spring with one that's 10% stronger than factory specs. Then check the rifle for long range accuracy. Many folks who do this are quite surprised.