Traditional Press Seating Die vs. In Line Arbor Press

[JPatzig]

I know this has been discussed before, but I'm wanting to squeeze out more consistency/accuracy with my reloads and I'm questioning the benefits of an inline arbor press style die. I've loaded for around 10 different cartridges over the past 5 years, exclusively using Hornady Custom Grade dies. They've served me well, but I'm shooting out to 1000y now (for fun) and wanting to tinker with "higher grade" reloading components. I've decided I'm going to get some custom Whidden dies made up from fired brass. When I spoke with Whidden, they actually stated the traditional press seater will produce less runout (over the inline die), due to the spring loaded collar that presses on the shoulder. But it seems inline dies are all the hype these days. The biggest positive feedback I see with inline dies and arbor presses is the ability to "feel" the amount of pressure applied. I understand that with the force pack on a K&M or digital data from the AMP Press will more definitively show variance in seating pressure. But what do you do with that information, and how does it help refine consistency and accuracy? Tweak reloading process until the variance is gone? Or do you remove the outlier reloads? Is it really the way to go, or do people just enjoy the ability to more easily feel and measure seating pressure? TIA

 

[cajun]

The guys using this setup from what I have seen segregate the outliers with seating pressure and use them for foulers or sighters at matches.

 

[Mikecr]

Any method or brands will work as well -while everything lines up in your favor.
But odds seem better with inline seating.
It isn't just low runout, but also consistent seating depths, as press flex/play is removed.
I've yet to run into an issue with Wilson inline dies, or Wilson die blanks chambered with my finish reamers.

If necks are normalized for friction, then seating force variance correlates with comparative neck tension (what matters).
Once you've seated bullets to identify outliers, I don't see where you can do anything but separate them out.
So instead of seating force (with bullets), I measure pre-seating force (with an instrumented mandrel die).
Here, I can adjust neck tension to match them all, before seating actual bullets.

Mandrel expansion is another contributor to low loaded runout, as the mandrel pushes most thickness variance outward, without a possibility of offsetting necks (like button expansion does). Then your bullets seat straight with well centered necks.

 

[RegionRat]

If you are willing to go down the 1000 yard accuracy rabbit hole, you are going to end up with both traditional threaded dies for a standard press, as well as an inline seater and arbor press. If the economy is broken by the idea of having both, you are in the wrong discussion.

One way to look at this is to imagine that you take the little arbor and inline seater to the range with ammo that has been loaded long, and run your depth testing while adjusting in real time.

As for the study of all the little details that contribute to seating force variations, your question answers itself. Yes, you will test your own process to determine what if any effect there is at the target, but the main point is that this (force feedback) is only practical with an inline seater to begin with.

Later on, you can decide if you use a regular process, or one that is sensitive to seating forces. Many run both ways, but still use the inline just before shooting, but after they have developed their process.

Runout has little to do with this since both methods can produce low-runout ammo (or high runout ammo for that matter).

Runout used to be a challenge when brass was low quality and required sorting and turning. That is still a small risk, but the quality of runout in brass has dramatically improved in the last 25 years to the point where you almost don't really hear about it any more. If your brass wall thickness looks like a banana, it almost doesn't matter what you do you will end up with runout. Starting with good quality brass is a given.

If you preload vast quantities of precision ammo and it must travel or be stored for travels, then you are probably going to want the inline seater and a small arbor along for the trip. YMMV

 

[Slick8]

Good info, I'm thinking of adding one to my rabbit hole....loading bench for the reasons stated above.

 

[JPatzig]

Thank you for the information, really helpful.

 

[cape cove]

A great inexpensive way to load good straight ammo ( which will rival inline dies, arbor press etc) is to use a Redding body die to size your case body and bump your shoulder to where you want it, a Lee collet die to size your case neck and remove spent primer and a good seater die to seat your bullet. With good brass no reason you couldn't get appx .001 bullet run-out. JME

 

[Mikecr]

Only thing I don't like about collet neck dies is the lack of tension adjustment.
I can make ammo as straight (as ANY) with bushing dies (which I can adjust size & sizing length with) and mandrel expansion.
I also use custom body dies -for shoulder bumping (only). These are bump dies.

Since I don't FL size, and only partial NS and ~1thou shoulder bump, my loaded ammo (off exposed bullet bearing) is typically lower in TIR than measurable (under 0.0005", v-block gauge).
If there were an Olympic reloading contest, this would be one of my areas of competition

 

[RegionRat]

Only thing I don't like about collet neck dies is the lack of tension adjustment.
I can make ammo as straight (as ANY) with bushing dies (which I can adjust size & sizing length with) and mandrel expansion.
I also use custom body dies -for shoulder bumping (only). These are bump dies.

Since I don't FL size, and only partial NS and ~1thou shoulder bump, my loaded ammo (off exposed bullet bearing) is typically lower in TIR than measurable (under 0.0005", v-block gauge).
If there were an Olympic reloading contest, this would be one of my areas of competition

Mike, Just FYI and not trying to persuade you to use a LCD, but their neck tension is adjustable if you are willing to obtain other mandrels.

While the Lee folks take their best guess at the diameter of their OEM mandrel, many of us used to make our own and Lee also offered a few alternative sizes as well. You don't have to stick to the one they supply.

As for runout, I went through all that fuss back in the dark ages and learned that if brass is made with wall thickness that is bad, you can only do so much to sort or correct it. If brass is made well, you don't have much of a challenge to keep your runout low. YMMV

 

[Mikecr]

If brass is made well, you don't have much of a challenge to keep your runout low. YMMV

This is true.
The root cause of our runout is sizing of thickness variance.
So the 1st step in making straight ammo is to measure brass thickness variance, and cull away offending cases.
2nd step is to reduce sizing of what remains.
For necks, don't excessively size, and never size donut area (FL sizing of necks).
For the same reason, avoid sizing of web areas.

Tension is a different matter that is not adjusted with downsizing beyond normal spring back (excess interference).
Neck tension is hoop spring back gripping force against an area of bullet bearing. It would properly be expressed in PSI.
Since the spring back force of brass is limited per given parameters, adjustment of tension is through area applied.
The area is seated bearing available for a sizing length to grip.
This is what I adjust with neck bushings, and I can watch it across a chronograph.
An exception to this is with neck sizing length beyond seated bullet bearing. That sets up bearing-base binding, and brings donut brass and shoulder angles into neck tension. While it presents higher tension, there is way more tension variance in it.