Project Resizing and Concentricity

[beartooth91]

This will be interesting to watch. From my experience, I think alot of the "which die/process works" will be determined by the difference in the neck OD of the sized case versus the sized case. Just makes sense to me that the more you have to move the brass, the more opportunity for "error" introduced by any process. That's why the first thing I do before buying dies is measure a factory round neck OD and then measure a fired case from the rifle. I select dies based on how much I need to compress the brass. Also, brass quality would need to be consistent across the calibers so you don't get any quality x process interaction.....I guess what I'm saying is if you want to test just the sizing method, you'll need to control as much non-die-related variability as you can or you won't get credible results - the results will be commingled with whatever factor you didn't control...That being said, I applaud you for doing the test.

Two things I hope you'll keep track of and report:
1. for each caliber - difference between fired case neck OD and sized neck (as per above)
2. Mark/number your cases so that you can discard one or two if the continuously show poor concentricity (i.e. high variation in neck wall thickness.

Elkbane

Good, clear suggestions....
The .243, 7mm-08, and 30-'06 brass are all Winchester; each caliber (brass) from one bag apiece, when I bought it. The .223 brass is Hornady. These were originally purchased as one box of loaded ammo with the the 52 grn HPBT. I got a good deal on the ammo and bought it for the sole purpose of using the brass.
As for case neck O.D.'s; I hadn't intended on reporting that, but, do have the data. As I've been purchasing Redding Bushing Dies, I've found out - the wrong way - one needs to know the fired neck O.D. (in addition to the loaded neck O.D.) so one can select an intermediate size bushing as most factory chambers dictate two bushing sizing steps for optimum concentricity.

But, one question for you - other than for bushing sizes, what's the reason for measuring fired brass neck O.D. when selecting conventional dies? I can understand it for bushings, but, for conventional dies I'm not seeing how it matters unless you know how much one manufacturer's die is going to compress the neck.......?