I have Remington .223 brass with .009 neck thickness variations, and the expander or a bushing die can have runout problems with neck thickness variations.
Even if the case neck remained concentric with the case body after sizing the bullet would be out of alignment with the bore.
By simply installing a high mounted Forster expander in my Redding .243 die it greatly reduced neck runout. And a Redding bushing die in the same rifle with neck turned brass produces more neck runout. And this is because of the amount the neck expands when fired and then need to be reduced in diameter when sizing.
You have postings with people not using a expander and not expanding the necks at all and their case neck looks like a wasp waisted pistol reload.
The expander is not the end of the world as many people think. All you need to do is polish the expander and lube the inside the case neck. And if needed use a Forster die with a honed neck to not overly reduce the neck diameter.
And using a expander die expands the neck on the upstroke of the ram and pushing down on the base of the case. This greatly reduces the chances of the case tilting when expanded and inducing runout.
Below a new RCBS expander and if not polished and the inside of the neck lubed it can pull the neck off center.
There are many things that can cause neck runout, your chamber, your brass and your dies. And its up to the person reloading on how to reduce any excessive runout for their type rifle and dies.
And now for a shocker, the average reloader without any gauges with a factory rifle can load very good ammunition with a simple and cheap Lee full length die. The locking collet when tightened centers the expander in the die. And with other type dies you can lock the expander down off center and induce runout. The expander is mounted higher on the expander spindle. This decreases any case tilt on the down stroke of the ram and simular to the Forster dies.
Bottom line, I'm not knocking competitive shooters with custom made rifles. But with a factory rifle with a SAAMI chamber, neck turning and using a bushing die can increase neck runout. And again the Redding bushing FAQ tells you to use their expander if the neck thickness varies .002 or more. And if you turn the necks you just have to reduce the fired neck diameter that much more.
Now look at the bushing die below and the clearance between the bushing and the die body. And this clearance will allow the bushing to tilt the more you have to reduce the neck diameter and increasing runout.
I sort of advocated not using an expander since it seems kind of dumb to size it down only to expand it back up. Sort of like drying corn to store it, only to add the water back if you're going make ethanol from it. Both necessary evils but still dumb when you think about it. I did an exaggerated example [sizing a case in a .25-06 die with no expander and seating a .264 bullet into that] only to show that it could be done with no adverse effect on either the case or the bullet.
I said in this thread or maybe another that I was not going to continue the practice of sizing a case with no expander and seating a bullet directly into that case. This is because Redding cautions against doing that if you seat your bullets with their competition seating dies. From now on my practice for 26 caliber will be to decap first, size the case sans expander and then expand with the .262 Sinclair carbide mandrel that I use for neck turning. With that I get 100% contact of the mandrel with the neck which should pretty much eliminate runout.
