First of all, ADG is just some of the nicest brass I have ever seen. it came in it's own 50rd box with a foam insert, sitting on top of the brass to protect the case mouth. The headspace and case length measurements were very good. No chamfering or deburring, per se, but very clean mouths. I loaded them directly with excellent results. Coincidentally the same accuracy node as my Lapua brass for 178 eld and varget, which is probably music to Buzz's ears.

So I believe consistent seating depth is one of the most important aspects and I have struggled to fully understand what affects this while seating. From the 200pcs of ADG brass, I had 2 cases loaded without powder. Humble brag, I think I am very consistent at operating the press for seating. About 20 sample from the last 80 loads were all within about +/-0.001" from 2.010" with my comparator. The 2 cases I pulled with the bullet hammer (i think it's called). They were both seated shorter and were off from one another.
Conclusion: I think pulling and seating another bullet messed with the neck tension. So think I am under appreciating the impact of neck tension on consistent seating depth. I assumed it was primarily a function of geometry/space. WRONG, i think.

Looks like it's a can of worms but I'd like to know more. I have tons of thoughts and/or questions:
1. I have a very standard hornady press with basic fl dies. I've looked into bushing dies and mandrel dies. The consistency at which my 223 loads are seating is really annoying me. I suspect it contributes some rando flyers. Bcause of the ADG, i now think inconsistent neck tension is causing my 223 problems. Which controls neck tension better; bushing dies OR a mandrel die? In my mind, no matter what the OD at the neck is sized to, then the mandrel will provide more immediate seating consistency. don't know though.
2. Seems there are more bushing dies withOUT an expander, a la LE Wilson and Whiddden, and some with it, such as Redding. I like not having to buy a whole mandrel set just to start off. Any experience with the 2 styles and how they contrast?
3. I got me a nice set of calipers. Is a micrometer actually a helpful tool for reloading?

Finally, I get this level of discussion is not "necessary" for me to make a good load. Already been through the normal "FL size with a nice die and just loading away" approach with good results. I am in the middle of long term pursuit to help me understand accuracy.

thanks in advance.

Redding type s bushing die is what you seek, use a wilson inline seater. Get yourself 3-4 bushings with a best guess + or - what a current loaded round measures around the neck. Use a micrometer not calipers as they usually have at least .001” error with slack.. shoot for .002” neck tension no more than .003” your run out will be near zero and your neck tension will be consistent.

Bushing die or standard die with no expander button then before loading run them on a expander mandrel with your desired tension amount mandrel and load.

I'm partial to the Nitride expander mandrels from 21st Century. I typically use graphite as a lubricant for this step after sizing the case with either a bushing or FL sizing die.

http://www.xxicsi.com/arbors-and-mandrels.html

For .223Rem I've found the Forster Bump Neck sizing dies to work well in conjunction with the 21st Century mandrel to yield consistent neck tension:

https://www.forsterproducts.com/product/bushing-bump-neck-sizing-die-kits-with-3-neck-bushings/
https://www.creedmoorsports.com/product/forster-bushing-bump-neck-sizing-die/-Forster

Currently I just spray One Shot almost exactly how Hornady suggests. They say hold it 45deg to get some lube into the neck, which it does. Would I need an additional step for lubing the inside more when using a mandrel?

No, that will work fine.

Two ways to get consistent neck tension....turn necks and use no expanders or use expanders. If it's something where I don't have necks turned then I typically use an expander, either the one that goes on the primer punch pin or an individual step like with a K&M mandrel.

I have a micrometer but I use it mainly for measuring neck thickness when I'm going to turn necks.

You're headed down the slippery slope KR

So much so that I don't set foot on it.

I don't shoot bench rest, so it isn't worth worrying about. 1/4 MOA or better without messing with this noise.

Normally I would say screw it but there is just something about this inconsistent seating depth thing that's driving me nuts.
Any thoughts on an expander mandrel from Porter Precision? Some f-class dude said they are great because they use pin gauges.

Okay...I may get pounded for this but my experience with seating dies you put in your press are less than impressive, some days I'd even call them junk. Example - my Redding 6.5saum seating die has a .003 window it will seat a bullet in...that is bull [censored], plain and simple.

So you have mixed two issues thinking they are one. Neck tension and BTO are two completely different issues.

To get the single best BTO consistency you can use a Wilson seating die, as tabjlr mentioned above. I've not found anything even close to doing as well as they do. Wilson doesn't make a 6.5saum die so I've ordered a blank and will ream my own because yes, it's that much better. Everything will measure the same length...but they all might not have the same neck tension.

I talk about your two options above on getting your neck tension consistent so I won't rehash that...but I will add...the 21st Century or K&M arbor presses with the gauges on them allow you to measure neck tension consistency. On comp ammo, I group like tensions and align them to relays...so each relays ammo is within a kernel of powder, within a range of neck tension and concentricity is as close to .000 as one can possibly get.

I don't know anything about Porter Precision. I have a full set of expanders and they match my neck turning mandrels (this is a necessity) so I use the same expanders and mandrels from K&M and you don't need a bunch of sizes per caliber, just get the standard one and more times than not, it'll provide .001 neck tension...which is generally what I run on most of my cartridges.

Judd, seriously thanks for the info. Now I'm leaning towards getting a mandrel expander die set may be the way to start. I get a feeling addition tools will follow soon. I will look into 21st century.

Are you shooting a cut rifled barrel that was chambered and threaded by a good gunsmith, barrel centered in the lathe to .0005"? Was your action faced tried? Has the action been bedded properly to the stock? Do you have pillars in the stock?

A giant "NOPE!" to most of that. A good thing these skills and tools should become even more useful when i do get to spend the exorbitant amount to get all that mess done. Right now my home bedded savage with a barrel I installed and my tikka will just have to do.
Just looking for more excuses to reload and shoot rounds!

NOPE

means you are on the wrong path with all this neck tension consistency to achieve your goals. Clearly your goals are holes in paper, very close together. Fix the machine before worrying about the last 5% of the ammo. What you're already doing with the ammo, and fixing the machine will get you 99% there. The subject of this topic is the last 1%. Thus the reason I don't even look at it.

You're stepping into final year of your doctorate. You never addressed the entire four years of the bachelor's.

Having shot so many absolutely terrific rifles, this topic makes me think "who gives a f**k?

Having shot so many pretty good rilfes, this topic makes me think "this topic isn't worth the trouble".

Having shot so many chitty rifles, this topic makes me think "what the hell is he talking about?"

Some people want to be doctors

While I agree with your thinking that’s it’s irrelevant, I also find myself going down rabbit holes when researching a given topic.

I hear what you're saying, fireman. But then no one but the rarest of us, those who can afford such luxuries, should ever pursue ling range precision. So I guess you're the guy who has to show up with the best stuff to compete at the highest whatevers.
Some of us just want to test the limits of what we have. All I had was a small Honda in the 90s. Supposedly I should have got a camero but that's what I had so it's what I made go fast.

I will answer your rhetorical question literally...the point is pursuit of knowledge. Plain and simple. Professionally and personally, I like running tests when possible to get understand the affects of something. And finally being deemed "of no practical use of fireman" is far from a definitive argument for me. I still got love for u but no one but Jesus mandates. So I will heed your suggestion as dismiss it because even your conclusion doesn't dismiss it as usable, just not substantial enough for u to care.

For the record, just arguing for the sake of arguing.

You claim to be the smartest guy in the room often, but clearly you are not. What I said went right over your head. All this neck tension B.S. is putting the cart before the horse.

Pillar and bed your rifle first. You're so smart, do it yourself. It will cost you $40 in parts.

Insulting prick.

I think what Jason is saying is that if you don't have a cut rifled barrel centered in the lathe to .0005" with a trued action face and bedded and pillar bedded stock, then any gains that you get from the neck tension consistency that you are chasing will not be realized. Take your Honda. If you put race gas in a bone stock Honda, you won't see a huge difference between that and 89 octane gas. However, take that same Honda, increase the compression, put in a high duration cam, and a turbo. Now you will see a huge difference between 89 ocane and race gas. Not a perfect analogy, but hell, I'm a finance guy, not a novelist.

Pot, meet kettle!

That’s a pretty damn perfect analogy in my opinion.

Just thought, u must not know alot of academics. Part of the problem in academy is that many jerk off doctoral candidates don't know their fundamentals. But that aside, I will twist your analogy and say it's more like a high level undergrad in rifle building/shooting wanting to know specific doctoral level knowledge in a related field. Cross disciinary studies often times fuels innovation.
The GI ingestible camera was made by a gi doctor having neighborly conversation with a aerospace engineer. I once had a very mutually beneficial relationship with a geology doc candidate because she was in our thermal fluid engineering class.

Yes of course and I understand. Putting a $300 on my bone stock honda would not have been as useful as some of my friend's tricked out ricers. Again totally get it. But If i were "Curious to see the effect of 89 octane on cars," then I imagine the most cost effect and efficient way to see it is buy some 89 and put it in the car I have. Sure someone may say that iI won't notice. Fine, I reply something like "your comment is well noted. I would like to be bullish enough to see for myself because your suggeswt of buying another car (orders of cost difference) vs just trying a gallon is just not what I want to do."

So in summary:
KR: I think neck tension is screwing up my seat depth. So what can I do about making my neck more consistent..
Judd: probably unrelated but here is what can be done abou tneck tension consistency.
Fireman: Not necessary unless u have top notch rifle
KR: got it, probably agree. BUT still I'd like to reserve the right to be the moron goes and sees for myself because my rifle aint dog-dingleberries and get a couple hundred mandrel set seems like a much more rationale 1st step than $2k rifle.
Fireman: waste of your time.
KR: i like wasting time shooting. gets me away from my kids for a little while and is hobby my wife doesn't mind.
Fireman: You're dumb for wasting the effort. I shall know go away and shoot my 7-08ai at my 800yd target while shanging up upside down on my mustache.
KR: Damn i wish i could grow one of those.

Where'd that come from?!

I missed this one. Again I never claim to be the smartest, just apparently the impression i give off. Fair enough but i still never actually claim to be the smartest.
Look, if I making you mad then you can simply not read it. I may insult people, but don't feel special. I do it to all in real life too just to lighten the mood. So sure I can very much be an insulting prick, hasnt' changed much since high school.

Btw, it is bedded. The barrel is crocked from the stock barrel channel. Won't learn much unless one tries. I ain't mad here.