Best thing I ever did: buy full length size dies. Pick a brass brand and stick with it. Send your sizer dies back to manufacturer with a dummy round, preferably your bullet of choice. Have them hone the neck of your die to 0.003 less than your loaded dummy. Don't use the expander button/ball when resizing your cases. Runout is about non-existent. Size them, trim them, deburr, and load them again. I anneal after every 2-3 firings now.
That's really good. With Lapua and most Norma, and not using the expander, my needle on my gauge pretty much doesn't even wiggle. With Win brass, I get up to .002. I don't think I'd see a difference with any of the shots with even 2 thousandths runout compared to zero.
I don't know for sure but I think runout plays a greater role when you load close to the lands. I can remember when I was doing a lot of shooting with my 308 using Federsl GM Match brass which I had a large supply. Run outs were all over the place, as high as .010", no matter what I did to it. I thought it was very poor brass, but it gave excellent results. With my MilSpec seating depth of +.150" it made no difference at all with 168/175 SMK's. That rifle shot .25-.4 MOA out at 600 yards very consistently. I did nothing to the brass except make sure the length was OK. The results were identical to those achieved with Lapua brass with run outs of .002" or less, and meticulously prepared. It's a very different story with my 6.5x284, 338, and 260 using VLD's closer to the lands. Brass prep makes a difference with group size and ES.
