Bushings, Mandrels, Neck Tension

[DocRDS]

I am having some confusion on all the resizing bith bushing dies and mandrels.

If I take a bushing die and resize so that my inner diameter is .306 (taking into account of course the bushing itself forms the outside diameter so Inner+2 Brass Thickness).

Now I take a .307 Diameter Mandrel and expand the neck to .307 for .001 neck tension.

So how would one get .002 neck tension, or even .003 (I realize the later is not common, but as an example). My understanding is that the mandrel gives a final inner diameter, so if I want .002 neck tension, I would need a .306 expander.

But almost all the mandrel expanders are a uniform size (from what I have seen--this could be the disconnect), but there are a ton of bushings. So now I'm lost. Even if I used a smaller bushing to squeeze the innder diameter to .304, the mandrel takes it back to the same inner diameter. Even if there is "spring" in the brass, the mandrel always produces the same inner diameter--so how does one then "adjust" neck tension, and what's the point of the bushing if the mandrel just undoes that step. (My guess is it doesn't which is why I'm a bit lost).

What am I missing.

 

[Dogtown]

There are mandrels that are a fixed diameter generally for neck turning, and then there are sized mandrels that allow you to expand the neck a specified increment. So a lot of folks these days will FL size with a bushing that's a bit smaller than their target diameter, then use a specific mandrel to set the final neck diameter. So instead of just relying on a bushing to size the OD on the downstroke and the die's expander ball to size the ID on the upstroke, it gets split into two separate (and different) operations.

Personally, I have a set of incrementally sized mandrels I use to adjust neck tension:

Caliber Specific Expander Mandrels

21st Century Shooting, Reloading products, Caliber Specific Expander Mandrels

www.xxicsi.com

 

[DocRDS]

OK Lightbulb. There ARE different size mandrels--I just got confused do to cross chatter between neck turning/expansion/etc..

My metallurgy is also not suspect. Was going crazy. Many thanks for the quick response/

 

[XLR308]

If you are using the neck turning set that many do including myself.
Use ether expander mandrel for .001" neck tension and turning arbor for .002" neck tension.

 

[308pirate]

@DocRDS check this out: http://www.xxicsi.com/arbors-and-mandrels.html and http://www.xxicsi.com/expander-die-body.html

 

[FFAZ]

There is a sinclair turning mandrel that is .002" under inside diameter as well. I made the same mistake initially and ordered the .307" expander mandrel, but if you look on brownells or sinclair, they do make one for .306" inside diameter

search for this part #: 749-019-019MB

 

[Gustav7]

If you are using the neck turning set that many do including myself.
Use ether expander mandrel for .001" neck tension and turning arbor for .002" neck tension.

Keep in mind OP, that brass springback can play a role in neck tension as well. While using either the expander or turning mandrel will most likely work for you, don't be confused if your brass has a little springback and your neck tension is reading a tad higher than the mandrel you're using.

For my brass right now, after its first firing, my expander mandrel(2 thou under) results in getting 2.5 thou neck tension, as the brass has a little bit of springback. I check my neck tension with Z-class pin gauges in half thou increments.

 

[whatsupdoc]

You can also just use a bushing die to set your neck tension and not use a mandrel at all.