Home Forums Hunting & Shooting Ask The Gunwriters Resizing without the expander ball

I got a Sinclair concentricity gauge ~17 years ago.
There was a note like a fortune cookie in the box, "You will probably find the expander ball is the problem."


I have not used an expander ball for a long time.

After 1) setting aside expander balls and 2) getting Lee collet neck dies, 3) the third big break through in my mind is turning the necks with a chucked live center in the tail stock. Cut the mandrel in the lathe and throw away after each session. The neck thickness runout will be that of the headstock bearings, typically less than 0.0001" with a modern lathe.

Clark, you got a couple pictures of this setup?

I do this too, it works really well. Instead of a live center though, I hold a cut down ram from an old Lee press in the tailstock chuck and use the appropriate shellholder. Some lube on the shellholder lets the case head spin easily, and after trimming, the case is pulled back off the mandrel by the shellholder so I can process all my brass without ever turning the lathe off.

With a live center, how do you pull the case off the mandrel?

Kingston: Clark, you got a couple pictures of this setup?




You can see a piece of hex 12L14 free machining steel is in the 6 jaw headstock chuck on the left. A tool bit is used to cut the steel to an optimum diameter for an interference fit with the inside diameter of the brass and to cut a shoulder to stop the case mouth. As long as this steel is left in original position, the runout of this mandrel is extremely low.
You can see the live center 3 jaw chuck on the right grasping the case base. The runout at this point will be ~0.001 ~ 0.003" but the base of the neck can elastically flex enough [through a lever arm the length of the case body] that this has very little effect on the neck thickness runout.




Yondering: I do this too, it works really well. Instead of a live center though, I hold a cut down ram from an old Lee press in the tailstock chuck and use the appropriate shellholder. Some lube on the shellholder lets the case head spin easily, and after trimming, the case is pulled back off the mandrel by the shellholder so I can process all my brass without ever turning the lathe off.

With a live center, how do you pull the case off the mandrel?

The live center grasps the base of the case with chuck jaws. The tailstock can crank off the case off the mandrel, if the Morse tapers are jammed in hard enough.
Years ago I was using a modified RCBS ram with shell holder in the tailstock per what I read in 2002 on Mike Bryant's website.
I was talking to him and he said he had a better method now. I wanted to try something better, but I could not remember what Mike said, and someone on the internet sent me a live center with a tailstock for other uses.... so I stumbled on this live center with a chuck trick..
http://benchrest.com/showthread.php...e&p=742156&highlight=#post742156
https://www.ebay.com/itm/3-Jaw-x-2-...k-Center-with-MT2-Arbor-New/291908770052

I think the one sent me is cheaper than this. There are lots of variations. But mine is MT2, so I have an adapter for my PM1236 lathe with MT3 tailstock.


After a few years of measuring neck thickness runout with a ball micrometer before and after turning.... Think how shocked I was to suddenly get 10X better than I had ever measured.
https://www.amazon.com/Anytime-Tools-Micrometer-Spherical-0-0001/dp/B01524DDIO

That makes sense, it sounded like just a live center, didn't realize you'd attached a chuck to it. (Don't know how much machining you do, but a "center" is a tapered point, what you have is really a live chuck in the tailstock.) That setup looks handy for a number of different things.

The ram and shellholder method works pretty well, but I've had to deburr the edges of some of the shellholders so they don't shave the rim on the off stroke.

Either way, this lathe method of neck turning definitely produces superior results in neck thickness.


One tip I use, that you might like as well, is to hold a small piece of 0000 steel wool against the freshly turned neck before withdrawing it off the mandrel. That removes those tiny burrs visible in your micrometer photo and burnishes the surface. Not a critical detail, just a nice finishing touch I like to use; fine steel wool is handy for all sorts of deburring and burnishing operations on the lathe as you probably know, especially with soft metals like brass, aluminum, and copper.

That can be done, but I have proven it is not idiot proof ....repeatedly.

For making 1" diameter bolt knobs of wood look fancy, I will do steel wool on a spinning object... carefully.

But for small diameter work I am using various grades of scotch brite pad. It is easier to keep from spooling around the work.

I just use a pinch of steel wool. If it gets caught (which I've never experienced when neck turning) it just pulls away, instead of taking a finger with it.

I got my Redding body dies today. Thanks for the advice.






P

This may be a dumb question, but is there a reason against just using collet neck die to size a dummy and determine if it chambers without resizing full length?

I have not been fl sizing unless it is needed to chamber?

This is the system that I use for quite a few rifles / ammo................I only use the body die as needed if cases grow too long.

MM

Going to try pushing the expander into the sized neck rather than pulling thru. How far are y'all backing off on the sizer die to be sure you're not reducing the neck after the ball passes thru?

None of it chambered. Needed sized.





P

You don't really need to back it off. You should be able to feel when the ball is all the way through the neck, so just don't raise the ram any more once you're there.

Yeah, that finally occured to me. Thanks

What might be the dumbest question of the day posted on the innanets - how do you push the expander ball through the neck but not pull it back out, just like a normal resizing step? It is quite possible I'm not visualizing this correctly.......

You do have to pull it back out, but in this situation the pulling out part isn't doing all of the work, most of it having been done in the push over part. Hence less runout.

This makes a huge difference in ammo concentricity, and thus precision. Shell holders pulling a tiny neck case over the expander ball, makes the neck bigger and bent.
1) Take the expander ball or stem out.
2) Resize the brass.
3) Put the expander ball or expander ball/ decapping stem back into the die.
4) Size the brass again, but only far enough to get the expander ball to go through the neck, do not downsize the neck again.
5) The case is now sized, the neck is big enough to seat and bullet and small enough to hold a bullet. The neck is only 10% as bent as it would be if sized and expander balling were done in one step.

The reason this makes a difference is that shell holders pull at an angle, while they push straight.

If your FL sizer die has been honed out to 0.002" smaller than the loaded ammo, the expander ball will probably not make the neck bent.

The reason for the expander ball existence, is that the neck in the sizer die is so much smaller than optimum that the bullet may not be seatable.

Other companies off the same service, but I have paid $10 to Forster to hone out the neck of a sizer die. I have done this over a dozen times.

To hone out a 25-06 die to my 6.5-06 specifications, that was a lot more than $10 and a lot of talking, as that is a lot of honing.
In 280AI [not offered by Forster], which I am building (4) rifles right now, I have honed out dies myself. That is to be avoided. Dies are hard.

If I understand the procedure correctly the case moves up, over and just past the expander ball. You stop right there and the internal dimension of the case neck is +/- the diameter of the expander ball. When the ball is pulled back thru the neck it is not expanding the neck any further, just traveling thru the corridor it just expanded. ??

It will still find some resistance, brass being a little springy.

There are two types of deformation, plastic, and elastic.
Elastic is how far it springs back, plastic is how far it does not spring back.

If you push the expander ball through, there will be plastic and elastic deformation.

But when the expander ball then pulls through, the interference is only the magnitude of elastic deformation.

Sure there is deformation pulling, but it is elastic and only lasts a second. No harm no foul on the pulling when done in a separate step.

As brass work hardens the threshold between elastic and plastic moves higher in applied stress. Having a Lee Collet neck die mandrel 0.002" smaller than the bullet or having a honed neck FL sizing die 0.002" smaller than loaded ammo seems to handle all variations of brass hardness.