mandrel for case necks...can somebody please explain

[WapitiBob]

I push my expander ball into the case neck then run it thru a neck bushing twice on new brass. Once fired brass I'll use a cpl neck bushings to get the neck OD down to .3115 then do the process I use for new brass. Works for me so far.

 

[milboltnut]

varying neck thickness will not be reduced by mandrels. Some say honed necks in FL dies will and prevent having to turn necks. Think about this way.... mandrels float in the die and center better than ball expanders even though some ball/decapper rods do " float ". Sectional diagrams show Forster ball expanders supported by the neck portion of the die size straighter necks. Redding expanders are longer than the typical balls in other dies but really don't make straight necks compared to mandrels. When you push a bore brush and rod in your barrel you can control it better when you push verses pull it out of the barrel.

 

[Hard rock]

NO! The guy provided options, what you do with them is entirely up to the end-user. The guy even caveat to stick with what works for you. I am not sure where the confusion is.

No confusion here , but I guess the big question would be how much less run out would you get all things be equal . That wouldn't necessarily be my question but anyone trying too improve their reloading techniques. I guess there is no way too know unless trying both ways.

 

[Ol' Red]

I believe that the idea behind mandrel use is to not introduce runout. Runout could be caused by many things and the use of a mandrel is not to eliminate runout that's already present.

Or, that's at least my take on it.

I have seen a Lee collet die remove .002 run out in a case neck. I am not saying that it will always work, but I had to give it a try myself. I still experiment with new stuff when I get the chance. I am sure that I will die of old age before I try it all.

 

[Redfoot Ranch]

Annealing after every firing, I use a bushing to size the neck down the least amount I need to in order get the ID expanded by the pin gauge of size necessary for my desired neck interference, with the least amount of work to my brass.

 

[Hard rock]

Annealing after every firing, I use a bushing to size the neck down the least amount I need to in order get the ID expanded by the pin gauge of size necessary for my desired neck interference, with the least amount of work to my brass.

Now that sounds like the way too do it . I may have too try that

 

[FEENIX]

No confusion here , but I guess the big question would be how much less run out would you get all things be equal . That wouldn't necessarily be my question but anyone trying too improve their reloading techniques. I guess there is no way to know unless trying both ways.

That's why he offered options for end-users to try and see what works for them.

 

[Varmint Hunter]

I have seen a Lee collet die remove .002 run out in a case neck. I am not saying that it will always work, but I had to give it a try myself. I still experiment with new stuff when I get the chance. I am sure that I will die of old age before I try it all.

My reference was to the use of a mandrel after the neck was minimally sized, not to the use of a Lee die.

However, your point is well taken.

 

[Redfoot Ranch]

this is pretty new and I might be a little slow.
I understand the theory of turning necks, neck sizing without full length suze and full length plus using a neck bushing to resize a neck to customize neck tension on a bullet.
However, I hear talk about using a mandrel that pushes into the neck. I don't understand why one would want to do that if you can resize the neck from the outside.
Can somebody walk me through this? I've reloaded my own ammo for 25 years, but this seems odd to me.

this is pretty new and I might be a little slow.
I understand the theory of turning necks, neck sizing without full length suze and full length plus using a neck bushing to resize a neck to customize neck tension on a bullet.
However, I hear talk about using a mandrel that pushes into the neck. I don't understand why one would want to do that if you can resize the neck from the outside.
Can somebody walk me through this? I've reloaded my own ammo for 25 years, but this seems odd to me.

I, like many, run chambers with "no turn" necks. I check neck thickness on new brass and will do a skim turn if it varies as I check it. I wait until it has been one-fired to do so.

I choose not to work brass any more than necessary. If your neck thickness varies, a bushing will push that variance into the neck ID and the OD round. The mandrel/pin gauge pushes the variance back to the outside making the ID round. I can feel it when seating bullets and intend to further test my practice with a small force pack arbor press and Wilson online seater on a new wildcat cartridge I'm beginning to load for. This cartridge starts with 8-10 thou neck runout after necking it down .060" unsupported .

I do what I have found works for me. This image is my first groups testing .1 increments at the bottom of a node found in 10 shots during initial load development. The first 2 here went into one ragged hole at a 100. I trued my ballistic app with that additional data. The last shot made impact on an MOA piece of steel at 800.



It works for me, YMMV.

Edit: wrong picture

 

[Ol' Red]

My reference was to the use of a mandrel after the neck was minimally sized, not to the use of a Lee die.

However, your point is well taken.

I misunderstood. Reread it. Got it.

 

[DUSTY NOGGIN]

I wish they made a 2 stage full length mandrel die

in say and arbor press type setup .. an extra tall body die .. with the top half of the body die being a mandrel guide

something you can send a mandrel through while being held in the die during length full sizing

imo turning is for neck clearance and cleaning up neck wall so a FL die will result in an ID on axis with OD

 

[Shawn Carverelli]

Shawn
When we pull a expander Ball back through the neck to set the final neck neck diameter we stretch the neck and introduce more runout.
We have learned that a Mandrel pushed into the neck does not stretch the neck and introduces much less runout.
The reason we use a Mandrel to expand the neck instead of relying on the neck bushing is because brass resists the last direction we move it in. Plus the Mandrel pushes the imperfections to the outside of the neck causing more consistent neck tension.

if I neck size with a bushing wouldn't it work the neck brass less?
So, let me see if I understand you all...
For best accuracy..less run out. You run a bushing over the neck while full length resizing the case body. Then- use a mandrel to push inside the case neck leaving the inside diameter the preferred dimension for neck tension..say around .002 less than bullet diameter.
Reasons being the expander ball on most dies increases runout- at least more than the mandrel does. Is this right?

 

[CBH Australia]

if I neck size with a bushing wouldn't it work the neck brass less?
So, let me see if I understand you all...
For best accuracy..less run out. You run a bushing over the neck while full length resizing the case body. Then- use a mandrel to push inside the case neck leaving the inside diameter the preferred dimension for neck tension..say around .002 less than bullet diameter.
Reasons being the expander ball on most dies increases runout- at least more than the mandrel does. Is this right?

I think you added a step. I would not put it in a mandrel die/collet die if I had used a bushing die.

A Lee Collet die has a mandrel of appropriate size to give an inside neck diameter. By sizing a fired case in this die you are using the press pressure to squeeze the internal fingers around the outside of the neck squeezing the neck in and it will be set to seat a projectile.

After a few firings or if the cases are from a different rifle you might need to full length size the case to reset factory outside dimensions. You can remove the expander ball use a body die and then you use your preferred neck die.

Some people like the Lee Collet die, it's an inexpensive die and budget brand. But it works for some.

Small investment with little to lose if you want to try it

I believe you can get a bushing die in a neck die you use a floating bush to squeeze down the outside of the neck.

I don't own but best I can explain it is a .308 calibre bullet needs .308" plus wall thickness times 2 to get a overall diameter. Let's call it .308+.003+.003=.314 ".
You might take off .002 to create a "desired" tension. Buy a die and a .312 bushing
Now, to case necks consistent thickness add a neck Turner in the budget.
But you might also buy a bushing a size above and a size below the required .312.

Equipment cost adds quickly.

I have invested time in reading. Various equipment and various methods will change results. How far you delve into it is up to you.

I'm not sure there is a right or wrong answer.

 

[CBH Australia]

Shawn, what sort of shooting do you do and what are you trying to achieve?

I've been loading about 25 years. I've had various results.

Loading equipment and technique will play a big part .

Patience and shooting technique might also help.

I'm far from competitive but I just hope I've explained it right.