Anyone using a arbor press and chamber seating dies? Is this technique significantly better than competition seating dies used in a regular press?

I use LE Wilson seating dies for everything except one caliber. On a hunting gun you probably won’t notice too much of a difference but in my experience your OAL consistency will tighten up and you have a lot more feel. I’ve got the 21st Century hydraulic press and a K&M with the pressure pack.

Chamber seating die?

The majority of my hunting rifles are match chambered. I use Whidden dies on a forester press and produce good results. Just trying to justify buying another setup.

I use bushing dies, with a wilson seater on a arbor press for rifle rounds that I shoot past 200 yards.
Runout is near perfect compared to a normal die set off the shelf.

Only one way to find out for sure, ordering the press and seating die. Its a sickness.

I get from zero to .002 runout just using standard Hornady or Forster seaters.
Of course that with good brass which is IMO way more important than what seater brand.

I use a regular Hornady seating die with an insert designed for my ELD-M bullets. I can think of about a hundred things more critical to premium accuracy than what kind of seating die you use. The only way that would become any type of significant factor is if you're like Judd doing benchrest and the difference between .1 and .2 MOA is important. Otherwise, I think most of us have much bigger fish to fry.

There are more items that will cause accuracy or inconsistency issues than having a custom seating die based off of your chamber. I don't see a benefit unless it's a wildcat round or something oddball. I can load ammo with zero to minimal run out with regular Hornady, Redding, or RCBS dies.

Id like to see the measurable improvement, so please report after you go through with it all.

Personally I don't believe the improvement will be there.

I believe the most beneficial aspect of using this type of seater die with an arbor press (with a force gauge) is the ability to segregate rounds that have unusually high or low bullet seating pressures. I believe this is the main reason why the Benchrest and F-Class shooters use them.

You can accomplish the same thing with standard dies and a rock chucker. Spending your time on anal brass prep will have more tangible results.

This^^^^^is the main reason I failed to mention. I use .284win to shoot competition when I can, I use 6.5x284 lapua brass (necked up with mandrel) after 4-5 firings I start to see some donuts so I ream and turn the necks, I'm hoping the arbor press with the pressure gauge will identify any inconsistencies in neck tension.

Are you sizing with Bushing die?

It will do what you are wanting it to show you.

This is why I am Judd's hero and reloading mentor.