Use good brass - Norma, Lapua, Winchester. Stay away from Federal, unless you are loading it once (once fired that is) and throwing away because the primer pockets open up. Use match primers. I use either Federal 210M or CCI BR2 (LR), and CCI BR4 (SR). Trim brass to the shortest length of the batch. Single stage press. Mine's a RockChucker. Use decent dies. I'm using Bonanza BR dies. As for powder, use what the rifle likes. I'm using RL15 for .308 (it hates Varget) and IMR4198 for .223. Good luck on the journey.
Most of what RePete wrote I agree with. We differ a bit on the trimming, but only by a few thou. Other than using bullets that the rifle likes (mine tend to like Lapua, Berger and Hornady), seated at the depth that the rifle likes (some like them jammed into the lands, some like a 0.020" running start and others are in between), the key to accurate ammo seems to be ... Runout. Strive for a total runout of zero; but accept nothing over 0.002". Buy a concentricity indicator from Sinclair or Forster. It's a very useful tool. Doing nothing other than sorting your ammo with this tool will make your groups more predictable by eliminating some of thos 'unexplained' flyers.
