My bore diameter is .348. How much larger should I make my mould? Several threads size to .351 or .352. One rifle needs .354.
My neck diameter is .377.
Normal suggestion is to size .001 or .002 over bore size.
I have two different lots of Winchester brass and the neck thickness for one is .012 max and the other is .011 max.
For best accuracy which is more important (factory and military chambers):
1. Bore diameter.
2. Using the largest bullet diameter the neck diameter will allow.

A bullet sized to .352 would give about .002 neck clearance, but over bore diameter by .004.
I know this is not a target rifle, but want to use this same concept for my military rifles. A local club has a cast bullet military rifle matches.