Too much case run-out: need some help

[Chaotik]

I have a run-out issue and need some help in understanding what is happening. Let me start by saying that I am loading a new caliber for me: 6.5 x 47 Lapua, and I am hoping to use this caliber for 600 yard F class.

The new brass has very little run-out (less than .001).

After the first firing and annealing, I use an expander mandrel (either the 21rst Century or the K&M mandrels – doesn't matter which) I have about .003 run-out. I neck turn and then use a Redding Full length bushing sizing die in either my Forster Coax press or my RCBS press. I seat my bullets with the 21rst Century hydro press. The run-out never goes away, and my final rounds have what I consider to be excessive run-out (about .003-.004).

My other calibers which I reload for (6BR and dasher) do not have more than .0010 - .0015 of run-out.
I check my run-out with either my Accuracy One concentricity gauge or the Sinclair concentricity gauge.

So I am perplexed and hope someone can help me understand what is happening.

 

[Chaotik]

Thanks, Donovan,

I guess I should add that after discovering this issue, I took several new pieces of brass (run-out of ~ .001) and ran them through the expander mandrels and that is when the run-out seems to start at ~ .003, and just never gets better.

 

[jonbearman]

Which press have you tried to do your expanding in?

 

[Cakes]

As Donovan stated you need to measure at each step of the process. Start at ground zero with a once fired piece of brass. This measurement will be a reflection of your chamber..ideally almost zero run-out. Each step after that will introduce some run-out you just need to locate and fix the step which is the culprit. Anytime one runs some brass thru a mandrel there is the potential to introduce some significant run-out unless one spends quite a bit of time during the set-up. I would be more concerned with the sizing and seating of a fired piece of brass that has almost zero run-out. FYI, make sure the mandrel is "floating" and use plenty of case lube. Good luck, Eric in DL

 

[Chaotik]

Which press have you tried to do your expanding in?

This has occurred with either the Forster Coax or the RCBS partner press.

The mandrels are floating and I use some lube (maybe not enough)

 

[amlevin]

I'd measure the case wall thickness all the way down to the case web. If the entire case is "irregular" it's going to be hard to keep a concentric and low runout neck on it.

I have a batch of .308 brass that the only way I can keep runout to a minumum is to use a Forster BR Full Length Sizing die. This die has the expander ball high enough on the de-priming rod that it starts expanding while much of he neck is still being held by the die. On the cases where I've turned the necks just enough to make them uniform in thickness around their circumference they come out nice and straight. It's great if you want F/L sized cases, not so good if you want fireformed cases to be neck sized only. That pretty much requires good, uniform, cases to begin with.

 

[BoydAllen]

You mentioned that your runout is induced by the use of an expander. What is the OD of your necks before and after expanding? Are you lubing your necks before you expand them? When you expand them, are you proceeding slowly?

In my experience, the amount of runout introduced with expanding is related to the amount of force it takes to insert the mandrel in the neck, which is influenced by lubrication, difference in diameters before and after, brass hardness and thickness, and the rate at which the mandrel is inserted.

Beyond that, I have found that letting the expander die or case float is counterproductive. I discovered this when comparing runout of .220 Russian cases that had been expanded up using 6mm on several different presses. My Harrell Combo has a very tight die and ram fit with very good alignment, and it is the best for this application. My Rockchucker was a little worse, and a friend's Forster was unacceptable for this particular use. (It worked fine for everything else.)

 

[bigedp51]

I'm with amlevin on this one, your bushing floats in the die and will not straighten the neck if it is off center. The Forster full length die will align the neck with the case body and the high mounted expander will not pull your necks off center. After this you can use your bushing dies, "BUT" if the bushing is sizing down more than .005 it can also induce neck runout.

Also with the Forster die you can send the die back and Forster will hone the neck to your desired size.

FL Bushing Dies vs. Honed FL Dies
http://www.accurateshooter.com/technical-articles/reloading/fl-bushing-dies-vs-honed-fl-dies/

Two-Step Sizing and Case Neck Concentricity
by: Germán A. Salazar
http://riflemansjournal.blogspot.com/2010/04/reloading-two-step-sizing-and.html

 

[bigedp51]

Stupid question number 247

Have you cleaned your shell holder and the slot in the top of the ram for the shell holder?
Back belly and both sides with a tooth brush and Q-Tips. (and the slot in the Coax Press)


I just ran out and bought 7/8 OD x 11/16 ID x 3/32 O-rings to hold my shell holder and the ram cutout for the shell holder was very dirty. I also bought more No. 17 O-rings to put under my dies lockrings.

In Glen Zediker book "Handloading for Competition" he tells you to let everything float and allow it to self center, he even shows a picture with a Sinclair expander die with a O-ring under its lock ring.

 

[Chaotik]

Ok. I just grabbed 5 new cases.
Neck OD before expander mandrel .2855
Neck OD after expander mandrel .287

Also checked run-out before and after:
concentricity before mandrel was .0005 - .0015
concentricity after mandrel was .0010 - .0025

Also, I switched presses and used my Redding Turret 7 press.

And shell holders and slot and coax were all cleaned (several times)

 

[bigedp51]

Chaotik

Question, do you have a standard non-bushing full length die.

If so remove the expander and size the case pausing at the top of the ram stroke for a few seconds. Now check the runout and see if it decreases the runout after using the mandrel.

 

[BoydAllen]

So, did you go slow when you inserted the mandrel in the neck? Also what did you use for lube, and whose mandrel did you use. The best that I have tried is a long tapered carbide one that PMA Tool makes. I like their die body too, but as little as you are expanding your necks, any of them should work. The long taper is a serious upgrade for expanding .220 to 6mm. The PMA die secures the mandrel against a square shoulder with a large diameter, axial set screw (down from the top of the die, against the back of the mandrel. For larger amounts of expansion, you can expand in short steps, reversing the handle between each one, trying to minimize axial thrust on the case. Also, when it comes down to it, I think that the alignment of the press, and the shell holder to the die threads matter as well.

 

[rocketron]

After the first firing and annealing, I use an expander mandrel (either the 21rst Century or the K&M mandrels – doesn't matter which) I have about .003 run-out. I neck turn

So I am perplexed and hope someone can help me understand what is happening.

if you are doing these steps in this order The expander mandrel is doing nothing to help the neck because the 21 st century is .001 under bullet dia. .264

Turning the necks would more than likely give you a uneven cut

 

[Chaotik]

I don't have a standard non-bushing die.

I inserted the mandrel slowly into the neck, and use Imperial size wax to lube the mandrel and inside of the neck. The mandrel was 21st Century's.

 

[lrgoodger]

Is there any possibility at all that the cases were over annealed? That results in case necks with the strength of a wet noodle and the slightest pressure from the expander will push the shoulder back enough on its thin side to wreck your runout.

 

[dkhunt14]

Are you sure you are neck turning them good? If you are not cleaning them completely up runout will show. A fired or sized case will show little to no runout and when you run a mandrel in it will push the thicker brass to the outside causing runout. Matt

 

[Chaotik]

Thanks for the replies.

I do not believe that the brass was over-annealed, as I used templaq and watched the temperature (which was only slightly more than what I use for my smaller 6BR & dasher cases.

Regarding neck turning, I used the 21st Century turner with the lathe. But most of what I know about neck turning is courtesy of what I've read in books and on this forum, and youtube. :-\