Playing with 'neck tension' is largely meaningless for factory rifles. I won't ever say 'never' about anything in reloading but worrying about neck tension is about as meaningless as it gets. Excessive 'neck tension' only makes it harder to seat bullets and that increases the loaded bullet run out and run out is detrimental to accuracy without increasing bullet pull at all.
What gets called 'tension' is really an interferrence fit, meaning the hole is smaller than the thing we push into it. Any neck hole smaller than one thou under bullet diameter is meaningless; it seems most think the extra effort required to seat in a smaller neck surely means it grips the bullet tighter but that's not true. The extra seating effort is just the bullet having to expand the neck to get in. When the elasticity of the brass is exceeded we have all the perminant 'tension' we gonna get, and that happens with the last thousanth or so.
One of the major reasons many of us get best accuracy with the Lee Collet Neck dies in factory rifles is that die is designed to obtain a sized neck about one thou smaller than the normal bullet diameter so we get less run out; works good too. (But a LOT of guys mess it up by sanding the mandrel down too small!)
