Forester full length sizing die- custom neck honing

[b00mb00m]

I am looking at ordering :

Full Length Bench Rest® Sizing Die for 6.5 PRC – 005349. I see that they do custom neck honing. ​

Full Length Sizing Dies

Order according to the profile of the specific cartridge.

www.forsterproducts.com

The FAQ wording confuses me.

On the site:​

Custom Neck Honing FAQ​

Q. How do I determine what diameter to hone my Sizing Die to?
A. Measure the outside diameter of your loaded rounds and subtract 0.004″.
This “hone-to” dimension will prevent the Die from overworking the brass, while enabling the EZ-Out Expander Ball in the Sizer Die to provide consistent neck tension on the bullet.

Wouldn't I want to measure a fired case and subtract 0.004" (or my brass neck thickness x2) instead of a "loaded round" ?

 

[TheOfficeT-Rex]

Wouldn't I want to measure a fired case and subtract 0.004" (or my brass neck thickness x2) instead of a "loaded round" ?

No. The neck must be sized down far enough that the expander ball makes contact and sizes the neck as it travels back up the case when the press ram is lowered. Measuring from a loaded round ensures the neck gets squeezed enough to get this treatment. If you measured from a fired round, you're measuring chamber clearance and may or may not get enough sizing to have the expander ball engage (or even to hold a bullet).

If you want to set final neck size without the expander ball, you probably want a neck bushing die.

 

[spife7980]

Wouldn't I want to measure a fired case and subtract 0.004" (or my brass neck thickness x2) instead of a "loaded round" ?

To expand on Rexs post, if the fired dimension is .005 larger than the loaded case then your .004 less than fired measurement would mean the case mouth is .001 larger than the bullet and the bullet would float in free air.



You want the die sized to make a brass to make a loaded round, not sized to the chamber. Your chamber size is sort of inconsequential in the die selection, so long as the chamber itself isnt smaller than the die itself which usually isnt the case. It shouldnt be the case on non wildcat chamberings so with a PRC you should be safe with any die.



If the bullet = .264, the brass is .012 thick (x2 to account for both sides of the cartridge) = .264+.012+.012=.288" loaded round neck diameter
If the bullet = .264, the brass is .013 thick (x2 to account for both sides of the cartridge) = .264+.013+.013=.290"


You can see that the brass thickness will dictate the diameter of the finished loaded round. In this situation I think that a .286 would be a safe choice for accommodating both neck thicknesses. It would be .002 smaller than your thinnest brass and .004 smaller than the thicker brass, meaning it would provide interference fit in both examples. The .012 thick brass would have the expander ball barely touch and really only work the thicker outliers more, the .013 thick brass would get a healthy .002 of expansion when the expander ball passes back through the mouth opening up its inside diameter to .002 below the bullet diameter.



I dont have a PRC so my case neck thicknesses were examples. measure your components and adjust accordingly. I suspect your magnum brass may be a smidge thicker.

In my creed you can see that if I went .004 smaller than the .297 I would size the neck down to .293. Thats .002 larger than a loaded round, it would never work.
The honed die sizes it down to .288, .011 of case work sizing it down from fired, but that resulting .288 is only .003 smaller than the loaded round diameter. When the expander is run though it gets larger by .001 to a .289 dimension. When I stick a bullet in the mouth it expands to .291 for a loaded round diameter. .

 

[b00mb00m]

Thank you so much for your time to explain this! I understand now!

 

[straightshooter1]

Thank you so much for your time to explain this! I understand now!

I've had my Forster FL sizing die honed and don't use the expander ball as I use an expander mandrel to get the neck tension I'm after. Doing this has given me very good results in terms of neck tension consistency and runout.

 

[b00mb00m]

Yes. That's the plan. I am going to get an expander mandrel as well.