Case Neck Concentricity

[ElmerThud]

Quote from Boozer in another forum:
Link from jimbires:

Quote: "High position expander ball- Some dies (forester I think) are sold with an expander ball mounted high in the decap rod. I believe the idea is that as the case is being withdrawn from the dies, the case mouth is still in the necking portion of the die, while the bottom is starting to be drawn through the expander ball. supposedly this supports the case, and aids in concentricity.

Since I decap as an independent operation, I think I can unscrew my decap rod to the point where this operation is the same (or close)".

I've been F/L resizing exactly this way for years & achieving very low case neck runout.
It's a system that works very well.
Plainly it's just inconsistent bullet seating runout that's the absolute pain!

 

[TackDriver284]

This is something I want to check on my dies, hope Redding has this feature. Good input.

Quote from Boozer in another forum:
Link from jimbires:

Quote: "High position expander ball- Some dies (forester I think) are sold with an expander ball mounted high in the decap rod. I believe the idea is that as the case is being withdrawn from the dies, the case mouth is still in the necking portion of the die, while the bottom is starting to be drawn through the expander ball. supposedly this supports the case, and aids in concentricity.

Since I decap as an independent operation, I think I can unscrew my decap rod to the point where this operation is the same (or close)".

I've been F/L resizing exactly this way for years & achieving very low case neck runout.
It's a system that works very well.
Plainly it's just inconsistent bullet seating runout that's the absolute pain!

 

[bigedp51]

bigedp51, I'm reading and absorbing what you're saying...might take a short time to fully grasp, but understand the point you make of difference between the two guages.
So, Question: Are you saying the RCBS guage runout reading should be halved?
i.e. a reading of say .006" is really .003"

Yes the standard concentricity gauge reads twice as much as the Hornady gauge. The Hornady gauge is reading the center line of the case from the primer flash hole to bullet tip.

The thing to remember when the case is fired the thin side of the case body expands more and becomes egg shaped. Sometimes this variation is case wall thickness will cause the case to warp and become banana shaped.

This is where you want to check the body of the case with the gauge and see if the bullet runout is coming from a egg shaped case.

My main point being with a full length resized case the case body has very little aligning effect on the bullet.

 

[ElmerThud]

Right ok, got that & am clear. I'm content my only issue is the alignment of bullet seating to reduce bullet/case & neck runout as far as poss.
As long as I can get consistently inside .0025" or better, I'll be happy.
Thanks for clarifying bigedp51

 

[TackDriver284]

Sorry to interrupt, but does the Redding dies have anything similar to the expander ball to help in concentric and alignment? If so, is there a link?

 

[ElmerThud]

Check it out on the Redding website Tackdriver, that's what I've done. When I get one, if it doesn't perform as expected, I'll sell it & move on, but it looks promising.
Redding Competition Seater die.

 

[truck driver]

Sorry to interrupt, but does the Redding dies have anything similar to the expander ball to help in concentric and alignment? If so, is there a link?

I don't know if they offer this on all their sizing dies but this is what I got from Redding when I had a decapping stem break on a set of 35 Whelen dies.
The cone shaped expander is new and the cylinder shaped expander is the old style.
I polished the shurface of the cone style by chucking it in a drill and spun it against a rubber polishing wheel that was impregnated with and abrasive to get a smooth mirror surface.

 

[TackDriver284]

Check it out on the Redding website Tackdriver, that's what I've done. When I get one, if it doesn't perform as expected, I'll sell it & move on, but it looks promising.
Redding Competition Seater die.

I do use the Redding Competition seaters and dies and S Type dies. What I mentioned was about expander buttons in sizing dies. I just wonder if my original buttons tend to pull the necks off a bit.

 

[ElmerThud]

Ooooops...sorry about that Tackdriver. Got carried away ordering my own seating die!

Been looking through the spares list for Redding sizing dies & there options of expander buttons available as truckdriver shows.

Google Redding die spares @ Midway.

The Redding tech site says the top can be polished, but we all know that anyway.
Can't help further on that just now.

 

[kraky1]

I've got the Hornady run-out gauge and corrector. I'm not really sold on it. The problem as I see it is you're measuring way too close to a holding point on the bullet. I've also seen the Hornady gauge give false readings on lead tip bullets where the lead is ever-so-slightly gubered up or slightly mal-formed. Then I have to scratch my head and wonder if every rim in every case is exactly perfectly made. AND I'm not sure I'm in love with the idea that moving a bullet in a case neck is going to leave you perfect neck tension all the way around.
I've seen the Hornady give the thumbs-up on low numbers on run-out on cases that I could see wobble just rolling across my table. I'm not sure it's a horrible tool but I'm not sure it's real valuable either... everyone else's mileage may vary!

 

[ElmerThud]

I've got the Hornady run-out gauge and corrector. I'm not really sold on it. The problem as I see it is you're measuring way too close to a holding point on the bullet. I've also seen the Hornady gauge give false readings on lead tip bullets where the lead is ever-so-slightly gubered up or slightly mal-formed. Then I have to scratch my head and wonder if every rim in every case is exactly perfectly made. AND I'm not sure I'm in love with the idea that moving a bullet in a case neck is going to leave you perfect neck tension all the way around.
I've seen the Hornady give the thumbs-up on low numbers on run-out on cases that I could see wobble just rolling across my table. I'm not sure it's a horrible tool but I'm not sure it's real valuable either... everyone else's mileage may vary!

I think you're probably right to avoid the 'correction' facility as I also think making that kind of a change will interfere with the consistency of round to round neck tension.
The objective really has to be the ability to load concentric rounds consistently, time after time.
Simply using the guage to determine you're actually maintaining that good level of concentricity.

Knowing what's wrong goes a long way toward resolving the issue.
For interest, I use the Sinclair guage to check my rounds. It's just a guage, not a correction tool.
However, I didn't realise until this thread, the readings have to be 'halved' to see the actual runout. Hey ho, live & learn LOL They don't exactly provide good instructions though!

 

[SJB358]

Great info fellas. I have the RCBS concentricity gauge and recently ordered the Sinclair neck expander mandrels so I can ditch the expander balls on most of my dies. After I got the concentricity gauge I immediately saw some variances which concerned me a little.

Hoping the mandrels help with my numbers since I believe in my case a decent portion of my problem is pulling the neck back over the expander dies.

I plan on monkeying around with this a little and seeing what I can do in order to improve my numbers.

 

[TackDriver284]

Great info fellas. I have the RCBS concentricity gauge and recently ordered the Sinclair neck expander mandrels so I can ditch the expander balls on most of my dies. After I got the concentricity gauge I immediately saw some variances which concerned me a little.

Hoping the mandrels help with my numbers since I believe in my case a decent portion of my problem is pulling the neck back over the expander dies.

I plan on monkeying around with this a little and seeing what I can do in order to improve my numbers.

Keep us posted on your findings, curious minds wants to know.

 

[TackDriver284]

Sorry to interrupt, but does the Redding dies have anything similar to the expander ball to help in concentric and alignment? If so, is there a link?

I don't know if they offer this on all their sizing dies but this is what I got from Redding when I had a decapping stem break on a set of 35 Whelen dies.
The cone shaped expander is new and the cylinder shaped expander is the old style.
I polished the shurface of the cone style by chucking it in a drill and spun it against a rubber polishing wheel that was impregnated with and abrasive to get a smooth mirror surface.

Thanks Truckdriver, I missed your quote , I'll check into that.

Thanks ElmerThudd for directing me back to truckdriver's quote. I was lost in space.

 

[ElmerThud]

Way to go Scotty. It's a lot of 'fine' engineering all this, but I'm certain it pays dividends keeping everything as straight as possible.

I'm hoping for a bit more of a small gain when my Redding comp. seater die arrives. I'm as sure as I can be that resizing the way I do is producing cases with only extremely small case neck run out.
It's getting the bullet in straight all the time that's triggered me on this one.

But, I am not getting into outside neck turning or bench rest behaviour. I just want consistent time after time small groups at 100 so I can be sure if I have to take a 300 yd + shot, the deer is going down.
Excellent help from all on this website.
Cheers ET

 

[ElmerThud]

Question for the knowledgeable:
I have a Sinclair Concentricity guage & am told the dial reading (rotation on the case body) should be halved to determine actual run-out. Is that correct?.....or not?

I'm also told the Hornady guage (because its rotation is from case head & bullet point) gives an actual run-out reading, so is different from the Sinclair. Is that correct...or not?

I'm trying to understand how if the dial pin is measuring from the outside of neck/bullet in both cases, why one can be different from the other.

I'm not an engineer or mathematician, so the questions I ask are because I'm short in the understanding department!

What I'm reading on the dial then, e.g. .002", really indicates .001" run-out & .004" = .002" !
So does this mean if the accepted standard of good reloaded ammunition is max .002" run-out and my dial reading shows .004" or less, the ammunition is fine, or is it the dial reading should not exceed .002"?

Sorry, not being simple here, but I haven't read anywhere a clarification on this issue.

Checking my case neck/body alignment, I find after F/L resizing, dial readings are usuually max. less than .001" & usually .0005".
(I put this down to brass thickness variation)

When bullet seating, bullet alignment is approx 50/50 (however careful I am) dial readings show .0015" - .006" or occasionally more, using the Nosler AccuBond bullet.

My seating dies are both RCBS Competition (which I've used for years) & in the last two weeks using a Redding Competition seating die.
Both dies have micrometer dial for accurate OAL, but, I cannot find one performing better than the other in seating concentricity and for some undetermined reason there can be a wide difference in dial readings on the guage - even though my technichque and brass is consistent.

So I'm looking for clues to making more consistent ammunition rather than half being what I'd consider excellent & the remainder a poor 2nd.

 

[bigedp51]

Question for the knowledgeable:
I have a Sinclair Concentricity guage & am told the dial reading (rotation on the case body) should be halved to determine actual run-out. Is that correct?.....or not?

I'm also told the Hornady guage (because its rotation is from case head & bullet point) gives an actual run-out reading, so is different from the Sinclair. Is that correct...or not?

I'm trying to understand how if the dial pin is measuring from the outside of neck/bullet in both cases, why one can be different from the other.

Read post #9 below

"168 BTHP bullet wobble"
https://thefiringline.com/forums/showthread.php?t=548430

The Hornady runout gauge holds the case like it would be held in the rifles chamber. Meaning in the chamber the case is supported and centered in the rear by the bolt face and by the bullet in the throat.

As you can see above a full length resized case has more "wiggle room" to center itself in the chamber. In either image above you can see where excessive runout, causes more misalignment with the bullet in the throat.

Meaning with a cartridge case with low runout readings the body and neck of the case do not touch the chamber walls. And have little to no effect on bullet alignment in the throat.

With a low runout full length resized concentric case the ejector is pushing the case forward and only the case shoulder is contacting the chamber. This means the bullet in the throat centers the front end of the case. With excessive runout the case body and neck have a guiding and centering effect and the bullet will not be aligned with the axis of the bore.

The military considers a cartridge with .003 or less runout as match grade ammo.

 

[ElmerThud]

Thanks again bigedp51..I'm sure I understand properly now.
I am completely happy with my F/L resizing with neck/body runout generally not exceeding .0005" and almost never exceeding .001"

It's always bullet seating where runout gets bigger.
I reckon that maxing at .003" bullet runout is achievable around 95% of the time and .002" maybe around 50-60% of the time, utilising all the care I can.

I've checked my new Redding Comp. seater against my RCBS Comp seater and neither is better than the other in alignment, but the RCBS bullet window is a greater convenience.
Both are excellent in producing consistent seating OAL.
Cheers, ET

 

[ElmerThud]

So, extending this query with regard to bullet seating run out, for hunting purposes the extent of run out I find doesn't matter much at normal ranges, but it might matter at longer range.

During my last reloading I carefully checked all aspects from start to finish and discovered; where I had run out of .008", so half that for concentricity to .004"... disassemble bullet from cartridge and clear propellant then resize.

Check case neck/body run out @ .0005" recharge & reseat the same bullet. No change in run out/concentricity. Still not really great.
Repeat the disassembly, resize/charge and use a different bullet: run out .002" concentricity .001"

So, although I don't have the instruments to measure the bullet to determine an issue, I must put the seated bullet run out down to bullet variables.
I think the difference is too much to be called a 'manufacturing tolerance' though.
Quite so much of a variable surprises me considering it's the Nosler AccuBond bullet I'm using.

Could I be wrong & have overlooked something? Maybe not measured correctly?
I don't believe so. But, I'm happy to stand corrected.

It's still something of a lottery though when I take a bullet from the box, seat & complete the round & discover my cartridges aren't all quite the same.

Just as a final point, it does make a difference in impact point and group size @ 100yds.
Not enough to worry a hunter at normal hunting ranges, but there is a difference.

This doesn't make me feel inclined to change my bullet choice, I'm a hunter, not a BR shooter, but it does make me think how much closer tolerance Nosler might be able to achieve...?

 

[SJB358]

I think most of my run out occurs during seating ET. I've used the Mandrels, checked the necks and an seeing about .001" or less. After seating I'm getting between .001-.006'ish depending. My Forster seating dies are crack on where as the RCBS dies are giving me the most trouble. Not sure where to go from here though.