In my experience with neck sizing, there has been no night and day difference in accuracy, rather an improvement on an already accurate load, the improvement was slight in most cases.
The caliber that has benefited the most for me with neck sizing was .338 win mag; It was not innacurate before. It head spaces off the the belt way down at the base of the case, the neck sized cases fit the chamber better IMO. At least that is what I credit the improvement to.
NRA Lifetime Member Since 1999
"I ask, sir, what is the militia? It is the whole people except for a few public officials." George Mason