Here is a bit of information that may be usefull. One thing to remember is that you will need to ream or turn your necks to a uniform thickness for best results and not use an expander button in your dies.
Leading benchrest die makers such as Neil Jones and L.E. Wilson solved the problem for precision reloaders decades ago by introducing dies fitted with interchangeable neck sizing and shoulder bump bushings -- dies that could be tailored exactly to the thickness of the brass in the neck. While L.E. Wilson focused on hand dies requiring the use of an arbor press, Neil Jones adapted the design to standard 7/8-14 presses. Both makers still turn out beautifully machined dies that are highly favored by precision reloaders.
What's interesting is that the interchangeable bushing die design has recently been picked up by major firms such as Redding and Hornady, making this advanced design more well known and more available to the average handloader.
What's the advantage of interchangeable bushing dies? Well, it's math time and you can easily make these same measurements with your own dies. In fact, you should. It's a very educational exercise.
The following measurements were taken from once-fired brass in a Model 70 Winchester .308 Featherweight, which was then sized in a standard RCBS full-length sizing die.
Neck diameter of the loaded .308 round: 0.336"
Neck diameter after firing: 0.349"
Neck diameter after sizing with expander button removed: 0.329"
Total reduction of neck after sizing: 0.020"
At this point, we have worked the brass down .020". Now we draw the expander button (measuring 0.307") back through the neck and increase the neck diameter of case to 0.335". In short, we have worked the brass down and then back up .026" (actually a bit more because of the brass spring back).
A More Modest Approach
With a bushing die, the outside neck diameter of the loaded round is taken as a constant reference point: 0.336". A hushing is selected with an inside sizing diameter 0.002" to 0.003" smaller than the neck of the loaded round -- 0.334".
Neck diameter after firing: 0.349"
Neck diameter after sizing with 0.334" bushing: 0.335"
Total reduction of neck after sizing: 0.014"
In this case, the brass in the neck has been worked down only .014", and the use of an expander button that can create distortion and concentricity problems all of its own has been eliminated. (Redding and Hornady do offer expander buttons in their die lines to add uniformity to cases that vary in neck thickness.)
The advantages of modern bushing dies that are available in increments of .001" are that neck sizing can be minimized, brass worked less, neck concentricity maintained, and expander buttons eliminated in most cases.
Uniformity of the brass you begin with is the real challenge. The most uniform brass lately comes from either Lapua or Norma. It's pricey, but it's quality. You need to begin with brass that varies not more than 0.003" in the neck. If it does, we suggest using Sinclair's power screwdriver system to turn your necks to a uniform thickness before employing bushing dies.
When neck sizing only with either bushing dies or standard neck sizing dies, the shoulder will progressively move forward, so eventually you will have to full-length resize or use a Neil Jones or Hornady shoulder/neck-style sizing bushing to set the shoulder back 0.002" to 0.003". In fact, Neil Jones recommends setting the shoulder back every time the neck is resized to maintain its fire-formed position. Jones, Redding and Hornady also offer full-length sizing dies that incorporate their interchangeable neck bushings.
Bushing dies represent one of the great advances in precision reloading. For the serious handloader, they're an invaluable tool for maximizing the accuracy of ammunition while prolonging case life. By all means send for the catalogs of Neil Jones, L.E. Wilson, Sinclair, Redding and Hornady, with their detailed descriptions of bushing dies and recommended reloading procedures.
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COPYRIGHT 2001 Gale Group