Expander mandrel ?

[Topwater]

Would someone please explain the advantages of using these over an expander ball? The videos I’ve viewed were somewhat vague. Which brands would you suggest? Thanks in advance.

 

[centerlineseal]

I've played around with a "Lee" internal neck sizing mandrel in 7mm-08. So far, I can not discern any measurable difference in group size vs. fresh Lapua brass. My understanding is that neck runout can be substantially less with the mandrel vs. and expander ball.

That said, I intend to use a mandrel on several other calibers as I like the idea of minimal working of the case neck.

Do a search here for instructions on use. Lot's of info available.

 

[miningshawn]

Watching this thread. I am starting to lean towards expanders (Sinclair seems to be a good one) a lot and would also like to hear about them.

 

[B23]

I like KM Precision and they make great stuff.

Expand Mandrel for Bullet Tension

Expand Mandrels for Bullet Tension expand the case neck so the brass will spring back to the correct size needed for seating bullets.

kmshooting.com

 

[jepp2]

Would someone please explain the advantages of using these over an expander ball?

My experience is that if your expander ball has to increase the neck OD by more than 0.002", it will pull the case neck and increase the TIR. That is even with using a carbide expander, lubing the inside of the case neck, and setting the expander high (so it exits the case mouth just as the neck comes out of the neck sizing portion of the die.

Using an expander mandrel doesn't increase neck TIR. If you want smaller increments of neck expansion, 21'st Century has them.

 

[JimSC]

When withdrawing a case and pulling the expander ball back through the neck the outer case walls of the neck are not supported by the die walls at that point. If the case cocks in the shellholder becasue of any irregularity of the case rim the expander ball can pull the case neck off center slightly. Using bushing dies with the expander ball removed solved 99% of any concentricity issues I had

 

[chromatica]

I use the Lee Collet die which contains an expander mandrel and also features petals that clamp down around the case neck to force the neck onto the mandrel causing it to center. The mandrel has a "decapping pin" that fits into the flash hole and only serves to align the mandrel with the center of the cartridge. Lee offers several mandrel diameters for each caliber, plus they will make you a custom mandrel for about $5.

 

[Bill Norris]

The K & M mandrels that I use to prep my brass for neck turning work great for me. As a starting point I normally run all my new brass over the mandrel to open and make sure all necks are uniform and then run it thru whatever Redding bushing that gives me @ .002 neck tension for that particular caliber and after firing I use the Redding F/L bushing die to bump the shoulders back by .001 - .002. I use this same method for my bench guns and hunting rigs as well.

 

[Ned Ludd]

The main difference lies in the fact that you're pulling the expander ball out through the neck from the inside, whereas an expander mandrel is pushed down into the neck from the outside. Without trying to go into any detail, the physics of these two actions are not exactly the same. Further, mandrels can typically be floated in the die/holder, whereas the the expander ball is usually locked down tightly within the die apparatus. There are also some differences in the shape of the typical expander ball and the [rounded] end of the mandrel where they enter the neck from top or bottom, and there can even be differences in the shape and/or diameter of different manufacturer's expander balls. Certainly many reloaders have gotten satisfactory results using an expander ball, so it is obviously possible to do so. However, I personally am not will to mess with them, and remove them from every die I own before use. I have the appropriate bushings and mandrels to achieve the neck tension (interference fit) I want, so the expander balls are unnecessary. Although you can certainly find less expensive approaches, I have had very good luck using the 21st Century mandrels in a Gen II expander die from Sinclair:

http://www.xxicsi.com/caliber-specific-expander-mandrels.html

All SINCLAIR INTERNATIONAL Products for Sale Online - 236 Products

Brownells has 236 SINCLAIR INTERNATIONAL products for Sale Up To 91% Off including Reloading, Tools & Cleaning, and Gear.

www.sinclairintl.com

 

[ronemus]

I use Hornady sizing dies exclusively because of their elliptical expanders. The profile is very much like that of a mandrel, so it is relatively gentle and doesn't increase TIR. I shoot a large volume and try to be efficient in my reloading processes; sizing with an expander instead of a mandrel cuts one step, which adds up to many hours over the course of a season.

 

[Uncle Ed]

If the expander ball is not centered in the die it will pull your necks off center inducing neck runout.

The Forster full length dies have a high mounted floating expander. With the Forster dies the case neck is held and centered in the die when the expander enters the case neck. And the floating expander self centers and does not pull the neck off center.

Below I installed Forster expander and spindle units on my Redding and RCBS dies.

I have found no difference in neck runout between using a separate expander die or using a Forster die. And see no sense in sizing a case twice when I can size a case once with a Forster die.

And I sort my brass with the Redding neck thickness gauge below. And with one turn of the case it tells you the quality of the case.

That being said people who neck turn already have an expander die and can get by without buying a Forster die. But with either method the quality of your brass and its neck thickness variation will effect your final neck runout.

Tech Line & Tips (FAQs)​

https://www.redding-reloading.com/tech-line-a-tips-faqs/146-concentricity-problems

Concentricity Problems​

a.k.a Neck Runout With Bottleneck Cases

Resistance to pulling your cases over the size button can indicate problems. A "squawk" says "shame on you", you forgot to brush the residue out of the necks. A hard drag can indicate that the top of the size button is not smooth. Don't be afraid to polish the top radius with #600 wet paper, but don't reduce the outside diameter or you can create an excessive bullet fit. Carbide size buttons are now an option also; they have a lower coefficient of friction.

We have conducted many tests over the years on the various factors contributing to concentricity problems with bottleneck cases. We have repeatedly found a definite correlation between the uniformity of the brass (or lack of it) and the resulting concentricity of the neck to the body of the case.

An interesting experiment also revealed that neck turning of brass that was intentionally sorted as non-uniform, showed little or no concentricity improvement when used in standard S.A.A.M.I. spec chambers. Conversely brass that was sorted and selected for uniformity remained uniform and concentric with or without a neck turning operation.

My comment, you can't make a silk purse from a sow's ear. And the image on the right is the pig's ear.

 

[JimSC]

I have had very good luck using the 21st Century mandrels in a Gen II expander die from Sinclair:

thanks, I have the Sinclair Gen II and I was wondering a while back if the 21st Century mandrels would fit

 

[jnyfeler]

I have Porter's gauge pin mandrels and they are ready to go out of the box. Available in .0005" increments; I would buy them again.

Mandrel Dies – Porter's Precision Products

www.portersprecisionproducts.com

Jeff

 

[PopCharlie]

+1 for the Porter pin die. It's what I use.
PopCharlie

 

[NorCalMikie]

The main difference lies in the fact that you're pulling the expander ball out through the neck from the inside, whereas an expander mandrel is pushed down into the neck from the outside

And, on every up stroke of the ram, the OAL gets longer and more trimming is needed. (more than needed)
Different size mandrels will let you choose the neck tension YOU'RE after. We learn as we go.
Not a fan of Lee reloading gear. Been around for a looong time but I've gone to better gear. Whatever works for you. Wore out 2 presses doing mil spec 5.56 and 7.62 brass with crimped in primers.
And if it wasn't for each of our own opinions, the reloading gear makers wouldn't be around long. THEY can be thankful we ALL don't think alike.

 

[JimSC]

When withdrawing a case and pulling the expander ball back through the neck the outer case walls of the neck are not supported by the die walls at that point. If the case cocks in the shellholder becasue of any irregularity of the case rim the expander ball can pull the case neck off center slightly. Using bushing dies with the expander ball removed solved 99% of any concentricity issues I had

a bit of an update. Since the time I wrote this I have switched from Redding S bushing dies to conventional one piece full length dies. The reason I switched is that I theorize that a non bushing die would be cut using a one piece reamer in a single operation similar to how a rifle is chambered. This results in the neck being perfectly parallel with the body of the die. With the expander ball removed the only way the neck could be tweaked is if the rim of the case is out of perpendicular and the case would tilt as it is being withdrawn bending the neck to one side. Cleanliness of all the parts is essential with no dirt or debris on the rim of the cases or the shellholder

I am going to get flamed for this but even the cheapest Lee FL sizing die with the expander button and depriming pin removed is capable of giving great results when followed by mandrel expansion. I also have taken to cleaning the slot in the ram where the shellholder goes and the shellholder itself . I also replaced the spring that holds the shellholder in place with a oring on the ram itself to allow the shellholder the maximum amount of float so the case can self align to the interior walls of the die with minimal influence from the shellholder

 

[Intheshop]

"One" advantage to the pushing in process(expander mandrel) vs pulling out(I'll call buttons to distinguish)

The mandrel can be stepped,and/or enlarging the output end of the tubing(case). With a pull through,you get what you get if it's a solid head button(typical pull through's as supplied by current manufacturers).

A Lyman M die "spud" is a good example. There's not only a second diameter step,you also can flare. You can adjust to get three different dimensional functions from one process. And change these independently in making them.

Making your own mandrels isn't significantly different from making pull through buttons. I don't think we've seen the end of pull through development though. There's a cpl things left on the table there.