If you decide to turn the rims down, turn them to .480 for a little more extractor bite. The 6.5x55 is .4803 and feeds and extracts well from the standard bolt face. When I build mine, I will go that route for the additional meat that the extractor will have to work with. I only turned 5 down for testing so I'm not out much, but my preference would be for more material left on the rim.