Reynolds, if your die only sizes the neck, regardless of what it's called, it's a neck only sizing die. Full length sizing dies reduce body diameters and also move the fired case shoulder back a bit when used properly. Sizing dies with their body dimensions the same as the chamber and don't touch the fired case body or shoulder are made by people who do not understand how a bottleneck case headspacing on its shoulder fits the chamber and why a fired case's body has to be held rigid in place while the neck's sized down to keep the case neck well centered on the case shoulder if best accuracy is the objective. You are only neck sizing your cases with that die. How it differs from other neck sizing dies is not known to me.
If that die sizes cases that produce better accuracy than some other neck only sizing die, there's some other reason that has nothing to do with the fact that its body dimensions are the same as the chamber body the fired cases come out of. Note that fired cases are a thousandths or so smaller than the chamber they come out of, so their body and shoulder will never touch your custom die's body nor shoulder; it's just another version of a neck only sizing die.
Virtually all the benchresters gave up on neck only sizing some years ago and have switched over to the full length sizing dies with bushings of the correct diameter for their case necks. Such dies keep the case neck well centered on the case shoulder but size the case body and neck down very little and set the fired case sholder back a thousandth or so. Sierra Bullets was probably the first place where enough proper tests were made with various sizing dies and techniques (including all sorts of neck only sizing dies) back in the 1950's. They've been using off the shelf commercial full length sizing dies ever since; nothing else sized cases good enough dimension wise to shoot their bullets into the smallest test groups. Nowadays, they use Redding full length bushing dies or standard full length sizing dies on their fired cases to resize them. Those dies work the same way and use the same bushings as the ones made by RCBS.
Therefore, 603country, I highly discourage your from coveting a die whose body dimensions equal your chamber in that area. Get a full length bushing die from RCBS or Reddingf then learn how to set it up correctly in your press. Then you'll be sizing fired cases the best way for best accuracy.
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Last edited by Bart B.; January 1, 2013 at 09:30 AM.