Best concentricity sizing method I have used

zeke: "Not all presses are the same. My Rockchucker does not have a floating die holder, or allow a locked down die to float (square up), so i float it before locking it up."
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on presses like the RC the float the shellholder allows is sufficient to allow the case to align itself to the dies.

Back to my OP. I believe neck misalignment occurs when the case is being withdrawn from the die and the neck is not supported by the die walls. Without a expander ball the neck is supported during the sizing operation both on insertion and withdrawal.

My theory is that when withdrawing a expander ball the neck is only contacted by a small amount of the ball when the case is being pulled down out of the die and at a point where the neck is not being supported by the die walls. The case is being pulled down by the rim contacting the upper part of the shellholder. If the ball has more friction on one side than the other or the upper part of the shellholder allows the case to tilt because of a uneven rim the neck could be pulled out of alignment by a small amount.

When using a mandrel the neck is expanded on the upstroke with the case head being pushed down against the shell holder base and less likely to tip to one side. A square casehead and shellholder definitely comes into play here. I like to flush the shellholder out occasionally with spray electrical contact cleaner or isopropyl alcohol

Just theory but removing the expander ball sure seemed to cut down on alignment issue in my bushing dies and going to the expander mandrel seems to add another layer of consistency. Going back to non bushing dies just removed one other variable which could throw the neck alignment out. Add in that I can get mandrels in .0005 increments and it really allows me to fine tune the process and I am a convert to two step sizing

Once again only applicable for shooters who are going for sub .5 MOA precision
 
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Houndawg, I'm just now experimenting sizing my cases with a Redding bushing die, while you have moved away from them sounds like. Did you ever try using the Redding die without the expander ball and size the necks with the floating bushings only?. Just asking because I was just now thinking of trying that.
 
Did you ever try using the Redding die without the expander ball and size the necks with the floating bushings only?. Just asking because I was just now thinking of trying that
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yep and it works great. Just make sure when you put the bushing in and tighten the little plug that holds it you back the plug out about a 1/8 turn or so. You want to hear that bushing loose enough to rattle a bit so it can center itself on the neck. It won't size all the way to the shoulder but that is ok. You can even experiment with only partially sizing the necks by using the same method.

The big reason I went to to non bushing dies is that my bushings would not get the necks small enough for using the mandrels. I would have had to buy 4 more bushings .002 smaller than what I was using. Since I had non bushing dies on the shelf I went that route

Redding S types rock :)
 
The only drawback to using a bushing die is the need to have a constant neck thickness. Brass thickness is not constant with all brands and machines within the brand. To get one size I would need to turn every case to the same size, and that would be removing a lot of brass on some brands, others not so much. The neck thickness issue is the only reason I don't just open my sizing die up to .001 or .002 under bullet size. If you remove your expander rod from your sizing die you will find that the sizing die is perfect. Like Hounddawg, I use expander mandrels to set the size from the inside of the case. Measure your case in each step of the process and you will determine where the problem is and come up with a way around it.
 
I neck turn on all my brass now. First time I did it I was nervous as heck but once I got past the first few cases I found it is really not that big of a deal. You only need to do it once. Now any new cases get sized and neck turned before the first firing. Just another step in the quest for consistency. Once again something only the super anal target shooter needs to worry about
 
No, I'm not afraid to or unexperienced in neck turning, I do turn my necks, but do not turn them to a size that fills a bushing. I have found as much as .005" difference in neck wall thickness from one bag of brass to the next bag, all unfired and reported to be sorted for weight, etc.
Working with a mandrel sizer you are sizing from the inside and does not depend on the wall thickness, using a bushing die you are sizing from the outside and the wall thickness governs the tension on the bullet, I don't want that.
Also, I find that neck turning is not a one time deal, when your cases start to look sooty check the run out of the thickness of the neck. I also recut the under cut at the base of the neck to prevent doughnuts. Some of my brass is into extended usage and seems to flow more.
 
Scatterbrain your posts make no sense at all

If want your brass to have a .012 neck wall thickness and use a .240 mandrel it does not make a darn what the neck thickness of the brass is out of the box. You will still turn the outside of the neck to .264 ( .240 +.012 +.012 ) . You may have to take off .0015 on Lapua and .002 on Peterson to end up with .012 neck wall thickness but neck turning is neck turning.

Turn you brass right the first time and it is a one shot deal and you will never get a doughnut. I learned how from reading one of Tony Boyles books. You might benefit by buying/reading it also and learning the correct way
 
Hounddawg, have you ever wondered what is the correct neck thickness is? Or do you assume that it's .012? I know another reloader that assumes it's .010. Look at you your chamber SAMMI specs on chamber sizes with +-, look at your case specs with +-, and then determine what SAMMI had in mind for the correct thickness and then ask the brass makes why they do what they do.
Just like with annealing, my aim is to preserve brass, not wanting to overcut brass is another way to do this.
You do realize that some new reloaders don't understand what side of the neck their dies work from and what affects the desired outcome.
 
SAAMI case specs are "voluntary" suggestions for commercial ammo companies. For example, 308 Winchester case neck specs sans tolerances is 0.01875" thick. .309" diameter bullet, .3435" cartridge neck diameter. Here's the specs....

https://saami.org/technical-information/cartridge-chamber-drawings/

People reloading those cases are free to use their own specs.

Same thing with barrel lengths plus chamber, bore, groove and rifling twist.
 
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Going by your last post Scatterbrain I have to wonder if you have ever turned a neck. A lot of brass is .012 to .013 straight from the box, I suggest you buy a good ball micrometer. many times the .012 is merely a 90% skim cut, if you know what that is.
 
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