JordanM,
Check with the gunsmith who built the rifle to see what the back end of his reamers measures. The Winchester brass is different (tighter) than the Lapua/Norma stuff. If I remember correctly from fellow competitors who have 6.5-284s a "winchester" chamber is to tight to accept Lapua/Norma spec brass. I can't remember the exact tolerences but is a known issue to be aware of.
I've seen both types shoot very well. It's just a few thousands differnce in thier brass specs to make for an aggrevating time when you can't chamber a round in a brand new chamber with brand new brass and start scratching your head and cursing your 'smith. Just simply match your brass to the chamber that is cut. I could get the actual specs for you if you would like them for future reference.
Steve