Case Neck Concentricity

[Rol_P]

In my ongoing search for the "Bug Hole" 30-06, 180 gr hunting load I have momentarily focused on neck concentricity of my cases. Broke into a new box of Nosler 30-06 cases and ran them over my RCBS concentricity gauge while some once fired cases were in the sonic washer.

New Nosler cases, with the case body supported in the gauge at the case head and just behind the shoulder, yielded 20 cases with the difference between neck high and low points 0.004" compared to 10 cases which were measured on the same gauge yielding 0.001" - 0.002".

Earlier this year I had attempted to "true up" the necks on new Nosler cases that were showing 0.005" of difference between high and low points, using my sizing die without bumping the shoulder back, and was unsuccessful. A Nosler Tech did send me 5 new cases for no charge.

The 20 once fired Nosler cases that came out of the cleaner all measured 0.001 or less difference when measured on the gauge. I will be loading them for load testing with IMR4451 and Nosler 180 Partitions.

What would you do with the cases showing the most, 0.004+" runout? Load and fire form to true the necks? Call Nosler again? Look for Norma and/or Lapua brass to compare? Any suggestions will be most appreciated. Thanks in advance.. Rol

 

[Dr. Vette]

I often use brass like that for fouling loads when I have a clean barrel and start out at the range. Some brands have more of this than others, and if after shooting, annealing and using the Lee collet die on it I can't improve it, then they stay as fouling load brass, or move to annealing test brass, or hit my scrap container. I just consider it the price of reloading that not all of the brass will be as good as I'd like.

 

[Finaddictions]

Did you run those cases over your expander ball before you checked them for concentricity? I've noticed the necks aren't perfect out of the box. Running them over the expander generally makes them show little to no run out.

With that said, I'd probably reload them for one go round personally and then check again.

 

[kraky1]

Not trying to be a smart aleck but running virgin brass over a run out indicator is an exercise in futility. Fire them one time and size with a Lee collet die and smile all the way to the bank!

 

[kraky1]

This just popped up on another forum....Good related read....


Campfire Kahuna

Registered: 06/03/04
Posts: 24684
A few days ago I picked up a bag of new Federal American Eagle 7.62x51 NATO brass. As part of the first time prep I ran the necks over an expanding mandrel (Lyman M-die) to round them out and make the hole size uniform. I then assembled fifty of them into an approximation of Lake City M852 match ammunition.

Of the fifty there were fourteen cartridges showing .005" or more runout on the bullet ogives as measured with my old Sinclair test fixture. The numbers were written on the case bodies.

After firing they were deprimed and lightly neck sized with a Lee collet die. They were then FL sized using a Forster die with a custom honed neck and no expander in place, trimmed, and finally expanded with the M-die to match the first loading.

The following pairs of numbers indicate the first and second loading runout of the cartridges:

8,1
7,2
7,1.5
6,1
6,1
6,1
6,1
6,1
6,2
5,2
5,1
5,1
5,1
5,3

At this point I have not measured the case neck walls for uniform thickness. Experience tells me if I do take that measurement the one that only improved from .005" to .003" will not be the one with the best neck.

 

[joelkdouglas]

You can sort for case neck thickness variance before loading the first time, but sorting for virgin brass concentricity won't tell you much other than those cases weren't perfectly round in transit.

I haven't found a bug hole hunting bullet 180 match yet. I've fired a good number of 180s from 4 different 30-06 barrels, including a Bartlein, a Rock Creek, a Remington, and a Winchester. All have shot acceptably, but no bug holes. If you find one let me know!

150/155s and 165/168s, though, I can get to shoot very well.

I would load the virgin brass with 59 grains IMR4350, put a 155 Sierra Matchking on top (loaded to touch the lands), and see how those shoot. That should be a pretty good baseline of your/your rifle's capability.

Then run them across the concentricity gauge, size with a Lee Collet die or a Redding Competition Bushing die, and load the 180s. If using Accubonds start around 0.05 off the rifling, if Partitions closer works, like around 0.03. 56.5 grains H4350 works fine, as would IMR4350, IMR4451, Ramshot Hunter, etc.

I think you probably won't see the accuracy of the Matchkings with the hunting bullets.

 

[ElmerThud]

It's never the best idea to check new brass. It really needs to be quickly run through a die, once fired with a cheap fireforming load, then F/L sized to 'fired case' headspace dimensions, in a properly set up die with the decap/expander correctly centered.
Then check concentricity & sort.

Pain the botty, but worthwhile!
Cheers, ET

 

[Rol_P]

Thanks for all the suggestions fellas. I will have to pick up some Sierra Match bullets and give them a try. I will be slowed down a bit by Family commitments but will continue the search.
Have a great day.. Rol

 

[jimbires]

ROL_P , a few things I do know on this is , your brass is the most true right out of the gun . everything you do after this can cause harm to your straight brass . you should watch runout after each step in your process , until you find what is causing your problem . I would not check neck run out on unfired brass .uneven neck wall thickness will cause the brass to look like it has more runout , neck turning fixes this .

here is a thread from another forum on this same subject . I've PM'd with mikecr on other topics in the past , he is a sharp fella .

http://www.longrangehunting.com/forums/ ... on-172776/

 

[truck driver]

jimbires; Thanks for the link. I read all 3 pages and now have a better understanding of case neck concentricity. It seems I have been doing the best I can by cleaning the inside of the case necks and dry lubing then before resizing . I still might order a custom Lee neck sizing die that uses a straight mandrel expander if you can call it that since it basically doesn't expand the case neck since it is sized down to fit the mandrel.

 

[kraky1]

If you talk to them about a custom die you should probably order an extra mandrel or two with just slightly different dimensions.
The standard manual will give you about .002 neck grip.... which can be a little light after you fired your brass a few times.
I have ordered a number of mandrels that are .0015 under their standard mandrel and love them... they pretty much mirror the same amount of grip you get with an FL die. There are a lot of people that think the ability to vary neck tension can add quite a bit to the Arsenal of finding accuracy in a hunting rifle.

 

[truck driver]

If you talk to them about a custom die you should probably order an extra mandrel or two with just slightly different dimensions.
The standard manual will give you about .002 neck grip.... which can be a little light after you fired your brass a few times.
I have ordered a number of mandrels that are .0015 under their standard mandrel and love them... they pretty much mirror the same amount of grip you get with an FL die. There are a lot of people that think the ability to vary neck tension can add quite a bit to the Arsenal of finding accuracy in a hunting rifle.

So your saying a mandrel that will give .0035 neck grip will be better than the .002. Also do you polish the mandrel as some do from what I've read?

 

[kraky1]

Like some other people have posted some times .002 is really not enough when your brass has lost its annealing.
There's been times when with the standard mandrel I've been able to push bullets back into the case a little bit.
And if you hang around some of the bench rest forums you'll find a lot of the top shooters believe strongly that being able to play with neck tension is almost as important as playing with seating depth trying to come up with the best accuracy for a particular rifle.

 

[joelkdouglas]

I agree, I have found annealing to be very beneficial when using the Lee Collet Die.

 

[truck driver]

Like some other people have posted some times .002 is really not enough when your brass has lost its annealing.
There's been times when with the standard mandrel I've been able to push bullets back into the case a little bit.
And if you hang around some of the bench rest forums you'll find a lot of the top shooters believe strongly that being able to play with neck tension is almost as important as playing with seating depth trying to come up with the best accuracy for a particular rifle.

Scotty has me annealing after every time I fire the brass so annealing is not a problem .

 

[ElmerThud]

When I learned to set my F/L sizing die to ensure best concentricity of case neck/body alignment & fired case headspace dimension, I stopped neck sizing.

For concentricity, set the die in the press & loosen the decap/expander rod.
Drive a lubed case into the die, then withdraw the case until you feel the expander ball tighten in the case neck & stop!
Hold the ram, keeping pressure on, tighten the decap rod.

Your resized cases should now all be pretty close to concentric. The only run out will be down to brass thicknes variables on the case neck and will be very slight indeed.

Cases resized this way will chamber absolutely smoothly and consistently - always!
Setting the die to fired case headspace dimension will significantly aid case life, along with annealing.
Cheers ET

 

[Darkhorse]

I setup my sizing die just a little different. First I remove the shell holder and clean it and the top of the ram very well, I don't want any particles getting under the shell holder. Then when I reinstall the shell holder I tighten the set screw just enough that the shell holder doesn't fall out. I want it free floating.
I remove the expander ball completely. Then set the die to where it just chambers a round but I don't tighten the set screw at this point. Now take a lubed, deprimed, fired case from your own rifle and put it in the shell holder. Now I take a flat ground washer of about .250 thickness and slide it over the case. Push the case into the die, the top of the case will center the size die just before the ground washer contacts the bottom of the die which helps further align the setup. Now while holding pressure on the ram, tighten the lock ring and the set screw.
Next I will size a couple of cases and check for chambering. If good I go ahead and size all the cases.
Now I screw the expander ball back in but go deep enough to expand the case without sizing. I leave the stem loose so it will float then go ahead and expand the case necks.
Actually I use a separate die for expanding and don't tighten the die or stem, just let them both float.
The stem will follow the case neck which is already aligned concentric to your chamber and will not pull it off center.
Like Elmer, once I got this process worked out for repeatable results I no longer neck size either.

 

[ElmerThud]

Way to go Darkhorse..
A small mention....I set my F/L die with a rubber O ring washer under the locknut & when the die is tightened down to specific marks on die & press, I can just pinch the die up into the exact sizing dimension I want.
No further messing with the die locknut & the die/shellholder both have just enough 'float' to aid centralising the case.
My de-cap/expander rod is backed into the die away from the case head, so has only a short reach just clearing case neck inside the case body and I believe less affected by any flex of the rod.

It's interesting to note, when I first looked at buying a concentricity guage, I thought it would be good to be able to correct a bullet if the guage read too much run out.
Then I thought, Really? Am I going to do that with each cartridge? - No, I want to eliminate the problem so no correction is required & just be able to check to ensure neck/body had minimal runout & when completed, satisfy myself all was well.

So, I just check with my Sinclair guage and find run out generally max at +/- .0005" which I put down to variable brass thickness at the neck.
Works for me and although a couple of extra operations are invloved in the reloading process, the end result matters more.
Good luck all, Cheers, ET

 

[Darkhorse]

One more thing... I turn all my case necks to approx. 85% just to remove those thick spots.

 

[Guy Miner]

You know... There are dies with NO expander ball? Just neck size the brass...

Works great.

Regards, Guy