Re: Need new dies.....
Obviously more than one way to skin a cat, but some things you do are just opposite with magnums and high pressure rounds.
However part of it is difference in SAAMI and minimum SAAMI chamber and tight neck versus factory.
If you are shooting a tight neck with minimum SAAMI chamber extra care is needed.
brass will flow and thicken AFTER firing and you will often find that you need to "clean up" turn after firing once or twice. Particularily in magnum calibers, if you did not neck turn down onto the shoulder of the case.
.001 neck tension often will not work for hunting rounds and magnums. They often want about .003 tension. .001 tension is not a guarantee of accuracy even for 6PPC guns, neck tension must be tuned for each gun and each load. Neck tension variations will really show up at LR distances versus short range. However, IF you do not have a tight neck and match barrel, doubt all that work will be even noticable unless you are running .004-.006 variation in neck thickness.
If you have plenty of time and it is factory barrel, then may want to test 10 pieces of brass before you spend a lot of time and effort for no positive results.