Start with checking everything on your rifle. Scope rings, base, and action torqued properly, etc. I once had a rifle that all of a sudden started shooting bad and discovered that the front ring had loosened at the base.
A good barrel and quality bullets are where accuracy begins. I usually see better results on target with Berger than Sierra, but have shot many half sub 1/2 MOA groups with Sierra.
Redding makes very good dies and there is nothing wrong with a Rockchucker. On some of my brass, I like to use a mandrel die to set neck tension. Annealing really helps with tension and the shoulder bump. Make sure you anneal BEFORE sizing.
My belief is that you can get good groups from almost any powder that has the correct burn rate window for your cartridge. I've seen some pretty amazing groups from surplus ball powders. Varget is a powder that a lot of people swear by, but I have used many other powders with succes. TAC, RL15, N140, 8208XBR, and H4895 may not give the highest velocity, but have shot well for me in 308.