in "Sierra's Highpower Rifle Reloading" (DVD) G. David Tubb, said you don't realy want over shiny (slick) brass, this will ad to rear thrust on the bolt face , you want the brass to "Grip" the walls of your chamber. you want clean, dry, oil free ammo and chamber , that got me thinking , how to get more "Grip" , so I added 1 cup of "Black Magic" Blast Meda, to some walnut meda , and ran for 1/2 hr , the brass came out lookung like it was bead-blasted, , I then loaded 20 rounds of that and 20 round of supper shiny brass , and went to the range , the brass that had been ran through the blast meda grouped better and there was less black ring around the neck (gas leak) so now I use blast meda on all my ammo for my bolt guns , , for my lever, auto's and hand guns I use just red walnut shell meda,
Note: after running through the "BLACK MAGIC MEDA" all brass is washed and rinse with hot water before they ever see my bench.