This is important, what diameter is your chamber? Please measure the neck on a fired case so we can determine how much your necks are expanding, and the measurement of the neck with a bullet seated.
If you have a factory chamber, the neck clearance will run anywhere up to .008" larger than your loaded ammo neck diameter, which is what the neck will expand to.
The idea of neck turning is to get consistent thickness, as you obviously know, but, unless you have a tight necked chamber that REQUIRES neck turning so the cases fit, there is very little to be gained, as other variables seem to cancel out any advantage that MAY have been seen with turned necks in generous chambers.
I have a turn neck and no turn neck chamber in 2 300 Win Mag barrels, both are tight with fired brass, the turn neck chamber runs .0025" larger and the no turn runs .003" larger than loaded specs. There is no discernible difference in accuracy whether I skim turn in the no turn chamber or not. The turn neck chamber only requires .0015" removed to give the correct clearance and to get them concentric, it is no more accurate than the other chamber, although they use totally different brands of brass.
Also, the actual thickness is not important, it's the amount of clearance that is, if you are turning .014" neck thickness brass down to .010", you may be introducing an accuracy reducing aspect to your ammo, large expansion of the neck is to be avoided, as overworking the brass will effect neck tension negatively, even if you anneal.
Hope this helps.
Cheers.
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