Expander mandrel vs neck bushing die for neck tension

[hoguer]

Trying to continue my reloading knowledge, and I’ve come up with a question I can’t seem to find a good answer to. It seems the consensus on using a bushing type resizing die, you can set your neck tension on your bullet by taking a loaded round, measuring the case neck, then subtracting and desired neck tension and viola you come up with a bushing size.
But when resizing brass using a bushing, or any type of die, you are creating a uniform surface on the exterior of the case, and forcing imperfections in brass thickness to the inside of the case mouth.
So why wouldn’t we use a full length, generic rezing die, or even a nice expensive bushing die that we can try to set neck tension with, and then run the brass through a expander mandrel, precisely choosing the neck tension and forcing the imperfections to the outside of the case?
Am I missing something in the thought process of a bushing die?

 

[spife7980]

So why wouldn’t we use a full length, generic rezing die, or even a nice expensive bushing die that we can try to set neck tension with, and then run the brass through a expander mandrel, precisely choosing the neck tension and forcing the imperfections to the outside of the case?

Many (most) do! The only time I really see someone using the bushing only is when they have turned their necks for uniform thickness, ie, there is no imperfections to be pushed one way or another. All bushing dies come with an expander ball and decapper, its the default configuration. You have to remove that to go bushing only. However with all things you can play, maybe you find that not having an expansion step makes no difference for you in your loads so that might save you a step. I used to neck size down only back before I knew better and was perfectly happy with its results aside from tight cases and whacking the bolt open.

I have always used normal traditional full length dies since I went to full length but I just bought my first type s bushing die that bullets.com had at a price that I could get the die and bushing both for the price of the die alone elsewhere. My traditional die sizes the neck down .008-.010 under loaded diameter before the expander ball opens it back up. I bought the bushing .003 under the loaded round diameter. That allows me to eliminate the over sizing by the traditional die but still allows for me to open it back up .001 with the mandrel for the ideal .002 of neck tension. With my old traditional dies with the expander ball gutted it is more work than I would like to get the mandrel back in for expansion. Hence my picking up the bushing that will eliminate that extra work.

 

[padom]

I use either a bushing with no expander or a honed Forster FL sizing brass .004 under loaded neck size then opening them back up .002 with an expander mandrel to give me .002 neck tension.

this makes very concentric ammo. I choose FL vs bushing neck die depending on caliber and gun.
need to push shoulder back I use FL. just sizing neck I use bushing neck die....

 

[digrazir]

I also use Redding bushing dies. After I anneal the brass, I use a bushing .001 less than a loaded round and after sizing the brass run a K&M expander mandrel through them. For instance for any 6.5 the bullet is .264. The expander mandrel is .263 and allowing for spring back .001 I have .002 neck tension. If you use a bushing .002 or say .003 smaller than your loaded round and run the brass through the expander mandrel afterwards you are just over working your brass unnecessarily. Donuts anyone! If you go on the Redding website they now also recommend using a bushing.001 less than your loaded round. Ray

 

[padom]

I also use Redding bushing dies. After I anneal the brass, I use a bushing .001 less than a loaded round and after sizing the brass run a K&M expander mandrel through them. For instance for any 6.5 the bullet is .264. The expander mandrel is .263 and allowing for spring back .001 I have .002 neck tension. If you use a bushing .002 or say .003 smaller than your loaded round and run the brass through the expander mandrel afterwards you are just over working your brass unnecessarily. Donuts anyone! If you go on the Redding website they now also recommend using a bushing.001 less than your loaded round. Ray

You use a bushing .001 less than loaded round and then you run a mandrel through it that then somehow translates to giving you .002 neck tension?
You do know spring back means exactly that, it springs back towards the original ID of your fired case neck diameter not shrinks in size....Ive been reloading a long time Ive never been able to produce or heard of someone producing numbers you are talking about. Following your above post, you take a fired piece of brass that usually measures .005 (unless your run a tight neck then .003) neck OD above your loaded round neck diameter. You than take a bushing .001 under loaded neck diameter and somehow your brass does not spring back, you then run a mandrel and that reduces your next size another .001 which in turn gives you .002 neck tension???

Those of us that use honed FL sizing dies and/or bushings paired with a mandrel either

A) Have Forster hone our FL dies to .003-.004 under loaded case neck diameter

or

B) use a bushing die with a bushing that gives .003 - .004 under loaded case neck diameter

Then we run a mandrel through the neck to open it up .001-.002 giving us a final case neck that provides .002 neck tension.

And no, reducing your case neck down .002 - .003 does NOT over work brass. It is well published that you dont want to size your neck down more than .005" in at a time or that can induce runout or over work your brass. Someone has fed you vudo.

 

[Diver160651]

To the OP, I tend to measure the loaded round then use only the bushing without the expander ball, just the retainer and decapping pin as they ship with both.

BTW -Neck tension is not measured very well by sizing methods .002 etc. Depending on the condition of the brass you'll experience various amounts of memory. I measure or judge NT by the seating pressure.. For a jumped round with large primer in and around that 308 type parent case I am looking for about 45lbs -- same case, with a small primer maybe 30 lbs.. If the round is over annealed, the seating pressure will be low with a bushing that has been working just fine, so then I need to use a different bushing.

FWIW - I have seen the .002 method, both with expander and without produce seating pressures between 10 and 120+lbs.. on a standard single stage, these differences are hard to even notice. Because most of use are not really paying attention to the actual seating pressure, neck tension kills our hand-loads often making their SD/ES far worse than premium factory match ammo that uses new brass. At short range we just don't notice, but at ELR and long ranges you certainly will.

In general, it seems often we don't measure enough to even notice we have issues. So all the voodoo aside, if whatever ones is doing is producing very low runout and very low SD's, great.

 

[DrainTheSwamp]

And no, reducing your case neck down .002 - .003 does NOT over work brass. It is well published that you dont want to size your neck down more than .005" in at a time or that can induce runout or over work your brass. Someone has fed you vudo.

If your fired case measures .005 over loaded round OD, how should one go about sizing the neck back down .003-.004 under loaded round OD with out resizing more than .005 at a time?

 

[padom]

in 2 steps

 

[padom]

most don't. that is just rule of thumb. I can tell you most can't shoot the difference

 

[DrainTheSwamp]

Ok thanks.

I’ve been using the expander ball on my decapping stem in my type s. Heard that can cause concentricity issues?

Is that why everyone uses an expander mandrel to set the final neck tension in a separate step?

 

[spife7980]

I’m using them to make it more consistent. I can vary how I pull the small ball through the neck and thus induce inconsistencies in how much different sections get stretched and for how long. The mandrel should provide a consistent diameter to effect it all the same amount in the same exact way. Thats my justification for it at least. I’m not worried about my concentricity.

 

[digrazir]

http://panhandleprecision.com/redding-bushing-dies-select-proper-bushing/

 

[Schralp]

Many (most) do! The only time I really see someone using the bushing only is when they have turned their necks for uniform thickness, ie, there is no imperfections to be pushed one way or another. All bushing dies come with an expander ball and decapper, its the default configuration. You have to remove that to go bushing only. However with all things you can play, maybe you find that not having an expansion step makes no difference for you in your loads so that might save you a step. I used to neck size down only back before I knew better and was perfectly happy with its results aside from tight cases and whacking the bolt open.

I have always used normal traditional full length dies since I went to full length but I just bought my first type s bushing die that bullets.com had at a price that I could get the die and bushing both for the price of the die alone elsewhere. My traditional die sizes the neck down .008-.010 under loaded diameter before the expander ball opens it back up. I bought the bushing .003 under the loaded round diameter. That allows me to eliminate the over sizing by the traditional die but still allows for me to open it back up .001 with the mandrel for the ideal .002 of neck tension. With my old traditional dies with the expander ball gutted it is more work than I would like to get the mandrel back in for expansion. Hence my picking up the bushing that will eliminate that extra work.

Great info. I’m still learning quite a bit about dies outside of the basic full length ones. I like the idea of using the mandrel to open up the neck .001” after sizing it down .003”. How can I be sure that it is only opening it that much. I ask because if the bushing sizes are unique, then wouldn’t that also have to be unique? Is it adjustable?

 

[padom]

Great info. I’m still learning quite a bit about dies outside of the basic full length ones. I like the idea of using the mandrel to open up the neck .001” after sizing it down .003”. How can I be sure that it is only opening it that much. I ask because if the bushing sizes are unique, then wouldn’t that also have to be unique? Is it adjustable?

You would know if it does by measuring the sized neck after bushing sizing then the sized neck after running the mandrel through it. The bushing you use yes, does play a part in your final neck diameter after using a mandrel due to spring back. You need a few bushings to play with to find the one that gives you .002 final neck tension after running the mandrel through.

 

[memilanuk]

Something else... it might be worth getting some pin gauges for checking the actual ID of the case necks after sizing and expansion. They're relatively cheap individually purchased off of Amazon. Or, if you load multiple different calibers, it might be worth getting a larger set in 0.001" increments and filling in with the occasional one in half-thou steps where warranted.

They aren't 100% essential, but generally you'll get a better 'feel' (literally) for the neck ID than you will just using calipers, plus you can also 'feel' some things going on inside the neck (like donuts forming) before they become a serious problem.