Concentricity question

[savageshooter86]

Yep that is what they use. They use bushing size 335, then run the mandrel through after. Giving about 2 thous neck tension.


I tried that method on my fired cases and it changed to 3 thous runout from 1/2 thous prior..

Just tried a 339 bushing(neck now measured 336)by itself and using the CoAx press and Whidden FL bushing die. Case went from 1/2 thous to 2 thous runout.

I have a factory chamber so it seems I will have to 2 step size brass if using bushing die. But them that makes me question how all the other shooters are doing this with factory size chambers and keeping runout low?

 

[22BRGUY]

There are a few squirrely things posted about this.
For one, firing cases does not cause runout. F/L sizing does not reduce runout. It's just the opposite.
Cases are as straight as they're ever going to be right out of a smoking chamber. Anything you do to them from there brings out the runout.
This is why it's best to do as little as required in sizing(for runout).
It's also why it pays to cull brass by thickness variance, right up front.
Second, it's a bad idea, and not needed, to turn necks after firing. Turn them correctly while new.
Fired necks are never again gonna fit a turning mandrel well enough for better precision.

Also, there is nothing wrong with this Sinclair runout gage: http://www.sinclairintl.com/reloading-equipment/measuring-tools/concentricity-gauges/sinclair-concentricity-gauge-prod37479.aspx
They merchandise it as a concentricity gage, but it's really a runout gage, which is just what you need to verify straight ammo.
If by mandrel, you mean this: http://www.sinclairintl.com/reloading-equipment/case-preparation/neck-turning/turning-expander-mandrels/sinclair-expander-mandrel-oversized-prod33134.aspx there is nothing detrimental in it's use. Another just the opposite as this pushes thickness variance outward so bullets don't have to(bullets are terrible expanders), and so they seat straighter.

You should be measuring loaded runout off bullets. This removes neck thickness variance(pushed outward by bullet) from measure.
New brass will always have higher runout than recently fire formed brass, unless your chamber is out of whack. There is no reason to measure/fuss over runout, loaded or not, on new brass.

Think you may have misunderstood what I was saying Mike....I'll take the blame for not being more clear but what I meant was that you don't get the benefit of neck turning until the turned neck has been fired in the chamber, especially when checking the run out of the case neck. Sorry for not being more clear.

 

[jlow]

So here is a question related to what has been posted. I ask because I don't know the answer but what I have been told before and what has been posted here seems to be in conflict.

The question relates to how straight fired brass should be coming out of the chamber. From what my understanding is brass with significant uneven wall thickness will banana after it is fired and this is why we cull new brass with this problem. Andrew says that his brass comming out of the chamber is 0.5-1 thousands and mikecr says the case is going to be as straight as they can be coming out of a smoking chamber. So how does this relates to the "banana" statement.

I posted that I had problem with the Sinclair gauge - this is a fact. The problem is it would not give reproducible reading. I have had no problem with either the Hornady or NECO gauge.

 

[boltgunluvr]

I am also curious if your Lee collet die is incorrectly adjusted. Mine is adjusted where I use a finger or two to neck size. Never have had any problems. I use Lee press & dies with a Hornady concentricity gauge. I have compared against a Sinclair and they're always close. I think we all tend to make things more difficult than really necessary.

 

[savageshooter86]

nope Lee die was adjusted properly. The collet had been smoothed out and lightly lubed. The fingers of the collet were also very slightly opened up(I mean barely did anything).

 

[22BRGUY]

So here is a question related to what has been posted. I ask because I don't know the answer but what I have been told before and what has been posted here seems to be in conflict.

The question relates to how straight fired brass should be coming out of the chamber. From what my understanding is brass with significant uneven wall thickness will banana after it is fired and this is why we cull new brass with this problem. Andrew says that his brass comming out of the chamber is 0.5-1 thousands and mikecr says the case is going to be as straight as they can be coming out of a smoking chamber. So how does this relates to the "banana" statement.

I posted that I had problem with the Sinclair gauge - this is a fact. The problem is it would not give reproducible reading. I have had no problem with either the Hornady or NECO gauge.

Hi Jlow
I'll try to answer your question the best I can with my experience so far.....other opinions or experiences welcome.
As far as brass with uneven or unequal cartridge BODY thickness, I can see how they may "banana" on the cartridge BODY upon being fired and extracted to some greater or lesser degree depending how severe the thickness difference is. That being said, I think much of the cartridge case neck run out can come from a strong ejector spring pushing on the side of the case head as it is extracted after firing and forcing the cartridge case neck to be pushed to ride on the side of the chamber wall upon extraction. I think it is a good idea to experiment a little with the ejector spring removed to see if that is what is happening when there is a fired case run out issue. I agree with Mikecr though that, upon being fired, and without the influence of a strong ejector spring affecting, that cases should be as straight as they are going to get. To be honest, I can't remember having a "banana" body problem from uneven body wall thickness that severe but can imagine the possibility in an extreme example.
Hope this helps.

 

[mikecr]

From what my understanding is brass with significant uneven wall thickness will banana after it is fired and this is why we cull new brass with this problem. Andrew says that his brass comming out of the chamber is 0.5-1 thousands and mikecr says the case is going to be as straight as they can be coming out of a smoking chamber. So how does this relates to the "banana" statement.

There is a big misconception out there that firing cases brings out problems.
It's not the firing,, it's the firing-sizing cycle that brings out the problems.
Now matter how much thickness variance there is, anywhere in cases, you don't bring it to runout until you size.
If you were to fire cases forever without ever sizing them, you would see no more runout than produced by your chamber(<1thou with my chambers). This is why I say cases are as straight as they will be out of a smoking chamber.
Also, firing alone does not harden brass. Hardening only comes from causing brass to repeatedly yield back & forth(firing-sizing cycle).
And finally, firing beyond needed to reach fully fireformed condition, does not move brass. Moving brass, means sizing it from one location to another. When you get donuts on the 5-6th reloading, it's because you're moving it there(aka FL sizing).

I've nearly tested these things with a fitted 26wssm. 30+ reloads, no neck sizing, or body sizing, other than shoulder bumps(35deg shoulder).
The necks were turned, and loaded runout has yet to reach 1thou off bullets(with the Sinclair). And seating forces as measured have not changed. No annealing or trimming will ever be needed.
Now the cases were initially culled to ~1/2thou variance in thickness mid necks, which is pretty good, and necks turned. But I am sure runout from this would still come out with any real sizing and no doubt it would grow with each sizing.
One other thing, don't think for a second that you can reduce runout with sizing. You can't. All you can do, the best you can, is add LESS runout with sizing(better & better with less sizing and eliminating issues).
In contrast, firing typically reduces runout -some. When Andrew sees .5-1thou of runout out of a chamber, that's the best from his brass at that point, unless there is some problem with his chamber. Sizing, from there, will only increase the runout.

I posted that I had problem with the Sinclair gauge - this is a fact. The problem is it would not give reproducible reading. I have had no problem with either the Hornady or NECO gauge.

The NECO can be setup like a V-block if you apply a stop to the casehead. Sinclair already has this. Hornady only provides greatly reduced readings instead of actual.
If you weren't getting consistent readings with the Sinclair v-block, and they improved with a NECO, the only real difference is the case stop, and this tells me your case heads aren't square -which is runout.
I don't have issues seeing my ammo as straight from the Sinclair. When I do, it's a matter of finding out what's wrong with my ammo(not the gage).

 

[savageshooter86]

So mike, at this point how would I sort my brass?

Since I didn't cull or sort when I first got it or before I turned necks. Now they are 2x fired

 

[mikecr]

W/regard to runout, you're past the point of culling, and you haven't prevented the causes.
For the bananas you've created there is no hope in fixing them.

If I were you, I'd take some of what remains as low in runout, and watch for where it grows. Fix that.
Aside from thickness variance, it could be the die, press, shellholder, seating, amount or type of sizing, measurement, chamber/throat misalignment, boltface out of true, excess pressure load, or a combination.
Bunch of stuff reloaders counter to make straight ammo. Many give up and go to generalizing that runout doesn't matter, or they pick up a neck bender that produces lower readings regardless of actual runout.
But once you work it out, you can make and keep straight ammo, and with multi cartridges -easy.

 

[jlow]

Thanks guys for the input.

As for the ejector causing runout, guess I can see the rational.

As for the firing/sizing and not firing causing runout, I don' quite understand the rational - more explanation would help.

 

[savageshooter86]

So for others reading this and myself, what do you say is the best procedure when you get new brass for culling/sorting prior to neck turning?

I know the sizing and seating step can add runout and those areas need addressing.

you said I had banana cases but how do I know this or if the sizing is the culprit? Don't you check the case body near pressure ring for this?

 

[mikecr]

I check thickness variance 4-5 places around new necks, mid point. The variance runs full length of cases, so this measure indicates enough trouble right up front. Regardless of brand, or cartridge, or the thickness itself, I don't keep any cases with more than 1/2 thou total variance round the neck.
You might also cull with departure in overall thickness nearing 1/2thou from the pack. I don't, as I turn necks and later cull by H20 capacity anyway.
Problem cases won't get by me.

Sizing is the action leading to bananas. Thickness/springback variance is the contributing cause.
Fireform your cases 3-4times with no body sizing. They'll be pretty straight(no bananas). When you see runout on these it's not the body, but whatever you're doing with necks/bullets. Shouldn't be much.
Then add body sizing if needed and watch the devil come out. That's when you can quantify the banana forming of your cases. It's a step change.

Be sure to use a stop on your neck measure:

 

[armaster]

For new brass all the prep I do is run through expanding mandrel, load and shoot. Only after it's fire formed to my chamber do I check the concentricity on the fired case neck, then again after sizing to see where your problem is.

 

[jlow]

I check thickness variance 4-5 places around new necks, mid point. The variance runs full length of cases, so this measure indicates enough trouble right up front. Regardless of brand, or cartridge, or the thickness itself, I don't keep any cases with more than 1/2 thou total variance round the neck.
You might also cull with departure in overall thickness nearing 1/2thou from the pack. I don't, as I turn necks and later cull by H20 capacity anyway.
Problem cases won't get by me.

Sizing is the action leading to bananas. Thickness/springback variance is the contributing cause.
Fireform your cases 3-4times with no body sizing. They'll be pretty straight(no bananas). When you see runout on these it's not the body, but whatever you're doing with necks/bullets. Shouldn't be much.
Then add body sizing if needed and watch the devil come out. That's when you can quantify the banana forming of your cases. It's a step change.

Be sure to use a stop on your neck measure:

Sorry for the slow response but have been on the road for the last week and so only connecting at night.

Very intereting as I would have thought that the firing/extraction would bring out the banana. Having said so, I've nerver measure runout of fired brass and how it change after resizing so I will check it out next time I do this.

Wow, culling brass with neck variance of more than 0.5 thousands seems pretty vigorous... Assuming one is using LaPua 308, what percentage of new brass would pass muster?

In terms of culling brass after firing/neck turn i.e. Andrew's situation, it would seem that one could still cull based on measuring body thickness variation using something like a NECO gauge?

 

[savageshooter86]

went to shooting buddys house today and we checked my sized brass with the Sinclair case neck sorting tool
http://www.sinclairintl.com/reloading-equipment/measuring-tools/case-gauges-headspace-tools/sinclair-case-neck-sorting-tool-prod36959.aspx

It showed very consistent readings and no more that 1 thous variation using the tool. This was with 1x fired cases that had been collet sized and Redding body sized. Checked the runout on the necks using the Sinclair concentricity tool and it was showing 1.5-3 thous runout. Same cases that had 0.5-1 thous on fire formed brass.

Going to shoot some brass and check runout using his press and die, then my Coax press and die.

I am no expert but seems some of this is caused by the necks coming from 344 to 334 when sized.

I will also check by doing 2 step sizing to see what we come up with.

 

[jlow]

Andrew,

The problem with fire formed brass is if your brass is not neck tuned and you have as yiu say as much as 1 thousand difference in neck thickness, that differnce in neck thickness is going to be internalized in the fired form brass, BUT externalized if you LCD the brass....

Think though this a bit and you will realize that the 2 will not be the same without neck turning.

 

[savageshooter86]

I will use the tool next time and check. My friend is who was doing it and not sure how accurately he was doing so. But this brass was neck turned.

 

[jlow]

Neck turned brass should easily be less than 1 thousnads in neck thickness variation.

 

[mikecr]

The 'neck sorting tool' you're using is terrible. And NECO's gage provides about as much given their claim of 'relative wall thickness variation of a cartridge case'. See the play on words here?
Anyway, neither measures thickness like a ball mic.

Also, you can't compare thickness variance with runout. They're not the same, but independent.
If your sizing necks down 10thou, then yes you're bringing out any and all devil in it. That's a huge amount.

As far as my culling standard, it's not as tough as it could be. If I FL sized, my standards would go tighter.
Brand of brass makes no difference here, and I don't care what brand perfect or crappy cases show up in.
It may come down to cost for some.
Lapua or Norma are very expensive, but I throw away less of them depending on cartridge/lot.
Federal or remington are dirt cheap but I'm sure I'd throw most away. Winchester's fairly priced for the cartridge I use it for, and it's good.

The best AND worst I've measured were both in lapua 6br, from different lots. So I'll buy a small box, measure them, if good I buy a bunch of that lot(enough for a barrel -after culling). Otherwise, I try somewhere else until finding good brass.
But it's not like I use a bunch of it. I've never had to replace brass used(by barrel). Only a new barrel get's new brass.

 

[savageshooter86]

Yep. I understand there is a difference in runout vs neck wall thickness.

I have a factory chamber. Just got new rifle so necks will be about 342 on fired cases. My loaded rounds are 3365

Anyone care to help turn my necks down? The last was my first attempt. They may be good.