what size should the neck expander be in relation to the cast bullet size. anyone try a few thousands smaller that bullet size and what were the results??
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what size should the neck expander be in relation to the cast bullet size. anyone try a few thousands smaller that bullet size and what were the results??
I typically exand necks with the NOE two step expander. I shoot for a top step just over sized diameter, and a bottom step at or just below diameter. Example: I size .44 magnum at .431", and expand using the NOE .433x.430" expander. The brass springs back some so the neck tension is higher than the listed numbers would indicate. Years back I tried a side by side comparison of .40 S&W using powder coated 180gr loads, one using the as-issued Lee expander (meant for jacketed bullets) and a shortened RCBS .40 cast bullet expander. If my memory serves, the smaller expander yielded groups about 20% larger, likely due to boolit swaging, though no leading was present using PC.
I have yet to wring this principle out in a rifle but I have a set of different NOE .30 caliber expanders. Plan is to find out eventually!
Last edited by KVO; 03-26-2018 at 11:55 AM.
The normal tolerancing convention used by the die makers is to make the expander plug 0.002" less than bullet diameter, or .306" for a .308" jacketed bullet. For shooting cast in most .30 cal. rifles a .308" or .309" plug works well without deforming soft bullets.
The Lyman "M" die step expander usually has the starting "step" 0.002" over, and the shank 0.002" under.
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I agree with the KVO and Outpost. I like a thou or two thou under boolit diameter for the neck expanding radius of the expander plug, and a couple thousands over that for the case mouth flaring radius. Then a crimp die to close up the flare, or roll crimp, as the case may be.
On any I have made, I usually shoot for .002" under boolit diameter, sometimes a bit smaller. So far, so good
This is the email I received from Lyman yesterday.
"The 30 Long M die comes with a 30R plug which is already .307/.311. We do not make a plug that is .306/.310. The next size larger that we make is .310/.314. Oversize/custom plugs are not available at this time."
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