I'm starting to load for PRS style matches and am full length sizing my 6.5 CM cases with a Redding bushing die. Is it also necessary to mandrel the neck with a mandrel die for proper neck tension?
Well that is .002 less than the bullet so it seems alright to me. If you wanted to open it up anymore a mandrel would be the tool to use.
A .262 mandrel through them as they are now might not do much for every piece but every once in awhile youll feel the odd one catch some so in that sense it would be beneficial. Thats how I mandrel my dasher, the mandrel doesnt do much to provide a measurable change but it does provide me piece of mind. Most other calibers I size .004 below and use the mandrel to open it back up.
So the only way to improve from here it to test different things and see whats best.
I full length size then mandrel. Like stated above only a few cases out of a batch will give you some resistance. For consistency sake those are the ones you’re looking for anyway. For cartridges like 308 where I have a lot of brass I just segregate those cases out as I batch cases by 50.