I use Lee collets for .303 brit and 6.5x55 and never had a problem with those. I tried rolling some hunting loads with my new Lee .308 collet die with 2x fired winchester brass. It seemed to size the necks to about 0.306" which I thought was a little loose but from my experience with other cartridges, seemed like it should be OK. I seated a bullet, the darn thing had absolutely no neck tension at all.

Does anyone have a good method for reducing the size of the madrel? Chuck it up in a drill and take some sandpaper to it maybe? Or should I send it back to Lee?