Mikecr,
So if I understand this correctly, As I continue resizing my Fired Brass even with the .267 neck bushing which was giving me .001 run-out variance, the more times I fired and then resized, the run-out would progressively get worse? This makes me have to ask........ How do you correct it? Would the Redding Competition Neck Sizing Die help to correct this?
Most reloading issues are better solved with understanding than a credit card.
I don't know for sure why your runout is growing the relatively small amount it is(nothing extreme). Could be multiple reasons.
But we could at least
begin at the root cause of runout; sizing of thickness variance.
-Thickness variance is inherent to brass manufacture and exists from webs all the way to case mouths. If you mark a case and measure a thicker portion at x-degrees around the case, this circumferential attribute will usually trend as you measure up & down the case. That is, separate from thickness generally decreasing from webs to mouths.
-Sizing is changing relaxed dimensions from one to another, and there is both yielding and spring back in this action. So supporting or even squeezing brass is not sizing, until done so to cause yielding, and this changes spring back.
-Given same ductility, thin brass springs back a bit less than thick brass.
-Ductility changes with each yielding of brass, and it's changing differently with sizing of thin brass -vs- thick (different yielding).
-Spring back variance, from thickness variance, can and will grow by amount of sizing. If more energy is repeatedly added(more sizing), runout will grow greater and faster. Is that what you're doing?
A benefit of neck turning is that you remove thickness variance in necks, which allows for partial length sizing of necks without causing runout -from sizing of thickness variance in necks otherwise (that much of it anyway).
This can still be screwed up by any other sizing(esp FL).. It can also be screwed up by equipment problems, but I've yet to see my bushings contributing(not really). There are a few tricks to reduce runout contributors.
If you want to mitigate most runout, you can cull out cases with thickness variance right from the git go. You can pre-seat necks using expander mandrels. You can adopt a plan that includes minimal sizing. You can smartly measure runout with each stage & cycle of sizing, fixing any method/equipment issues.
Does runout matter? I think it's a local matter, and not so easy to answer otherwise. The cartridge & chamber would have to be considered into it. It could be no more isolated in testing than ballistic coefficient from field drops (filtering through noise).
Opinions:
I doubt it matters in sloppy chambers, and think it would in low clearance chambers. But on the flip side, sloppy chambers lead to greater sizing leading to higher runout, and opposite of tighter chambers. A wash there. I think fast powder cartridges remove runout before it matters. I believe the notions of ammo centering with chambering is hogwash, and that the affects of runout(where seen) has nothing to do with where bullets are pointed w/resp to bore centerline. Here, I believe it's a matter of chambered tension points, varying barrel vibrations as an abstract.