28 Nosler runout issues

[Toydy]

Hey there guys, I'm after some help with runout in my 28 Nosler loads.
After firing my case necks have around 3 to 4 thou runout. Re-sized brass necks have 4 thou runout. Loaded rounds have around 4 to 5 thou runout. Is it my re-sizing die?

 

[fiftybmg]

A quick test is to completely remove the entire decapping / neck expander assembly from the sizing die, and full length size one case. This means the bottom of the sizing die must make good contact with the shellholder, not just a shoulder bump.

Measure the runout.

Re-size again with the decapper / neck expander assembly in place, and measure the runout.

This will show if the neck expander button is pulling the neck one way or another.

If it is, you can polish that expander button or ball with 1200 grit wet sandpaper, on a lathe or drill press. It should improve the end alignment.

The best solution is a Redding body die, and a Lee Collet neck sizer, provided they are made for your caliber.

Otherwise, you can try a neck sizing mandrel instead of the Lee Collet sizer, and size your cases without the decapping / neck expander assembly. The mandrels are available in any size, and go with a mandrel body die.

You'll need a universal decapping die if you go that route.

 

[Toydy]

I forgotbto add, I don t use the de-capping stem in the die, I remove it, then use a sinclair mandrel.
Sorry for the admission

 

[L.Sherm]

Sounds like most of the runout is on fired cases, I would suspect crooked chamber.

 

[L.Sherm]

Really uneven neck thickness will give you higher runout numbers, can you trim a neck then fire the case see if that helps.

 

[Savage 12BVSS]

Sounds like most of the runout is on fired cases, I would suspect crooked chamber.

Sure could be as thats terrible runout on once fired chamber formed cases.

Really uneven neck thickness will give you higher runout numbers, can you trim a neck then fire the case see if that helps.

What brass are you using?

 

[fiftybmg]

I forgotbto add, I don t use the de-capping stem in the die, I remove it, then use a sinclair mandrel.
Sorry for the admission

If you full length size with no decapping assembly / neck expander in the die, and still have runout, then try your setup one more time with annealed brass and

1. get hold of a different die, re-measure
2. size it on a different press, re-measure

 

[Toydy]

Thanks for the help guys.
I was thinking crooked chamber as well but the case body is pretty much no runout. I have skim neck turned so I may have to go a bit deeper with the necks. I am using Bertram brass as it was the only brass I could get. The brass was annealed.

 

[25WSM]

If it comes out of the gun crooked then it's the chamber. Normally a full length die will straighten it back out. It will be crooked again when fired. A neck die normally will not. If you put crooked brass in a Lee collet die it will come out crooked still. The collet die has low run-out numbers on straight brass going in and coming back out straight. Is your die a full length or neck die?
Shep

 

[Toydy]

The die is a redding full length die with the decapping stem removed.

 

[L.Sherm]

Thanks for the help guys.
I was thinking crooked chamber as well but the case body is pretty much no runout. I have skim neck turned so I may have to go a bit deeper with the necks. I am using Bertram brass as it was the only brass I could get. The brass was annealed.

Even though the body is straight it's not concentric to the bore that's why the necks are crooked.

 

[Ed AO]

Have you tried it with the stem back in with the expander ball?

 

[fiftybmg]

If it comes out of the gun crooked then it's the chamber.

Before changing anything, get somebody else to verify what you are measuring with their own equipment.

I'm not understanding how a chamber can be crooked, unless you clamp the action in a vice and bend the barrel back 180 degrees.

The chamber is made from a reamer. A reamer is one piece. If the reamer was bent, it would be un-usable.

The only way possible I can think of to produce a crooked chamber is to cut the body only first, without the neck being cut, then go back with a different tool to cut the chamber neck, and remove and replace the barrel incorrectly on the lathe between tool cuts.

Which is impossible, because chamber reamers are only ever one piece.

How does a chamber get crooked ?

I understand how a chamber may not be perfectly aligned to the bore, but not how a misaligned chamber "bends" the brass. The chamber is straight, why does it "bend" the neck ?

Runout on fired cases is normal. Chambers are cut to different tolerance, and fired brass will have runout. Two pieces of brass fired in the same chamber can have different runout.

The measuring of runout with the concentricity gauge is indicative, not actual. Your finger pressure rotating the brass induces runout. Press a little harder, and see that dial move further. True runout is measured on a lathe, and is limited to the runout of the lathe itself.

If you fire brass, and your runout gauge says 4 thou, then size your brass and your runout gauge says a different number, you only have a comparison between what it was, and what it is, not a true measurement.

I'm sure the experienced machinists have a chuckle at us when we talk about mechanical precision and these hand operated tools in the same sentence.

 

[kfreeze]

I need some more info.
What brand of brass are you using?
How many firings on it?
Has it been annealed?
Has it been trimmed?
What are you using to measure concentricity?

The reason I ask this stuff is because on my nosler 28 nos brass, I noticed that the neck are real thick and real hard. Some 28 guys (including me) like to anneal their case necks every reloading. It makes a difference. Also if you have a hornady concentricity tool like I do, and the necks aren't trimmed square and only checking the brass you could see some of that. If you are measuring the concentricy of the brass neck and the neck hasn't been completely cut all the way around, you will see that as well, because the expander mandrel will push the imperfections to the outside where you are measuring. Just some other things to consider.