Concentricity??

[Dragoon300]

.004" total indicator run out is only .002" out of concentricity.

 

[Rob L.]

If 4thou eccentricity on a 'Hornady Concentricity Guage', then your actual runout is a lot higher still.
It's getting up there

How do you figure that, I guess I don't understand? Four thousands TIR runout is .004" TIR runout... meaning it's .002" off center. Are you saying the Hornady indicator or tool is no good or something?

 

[Rob L.]

.004" total indicator run out is only .002" out of concentricity.

Yes, I agree.

 

[Mikecr]

As for eccentricity: a banana can be centered on axis, then presenting as concentric.
But you don't want to make and chamber bananas. You want to make STRAIGHT bananas (full length).

So what you want to see with your gauge is everything NOT straight.
You want to see the worst of what your ammo is to a chamber.
This is provided by measure on a v-block. It is concealed on a neck bender type gauge.

For analogy, pretend a banana is a simple metal arch spinning between two centers.
You want to measure peak deviation from axis (or out-of-straightness).
Would you measure this near one of the arch's centered ends, or would you measure in the center/peak of arc?
The Hornady puts an indicator near a centered end.
A v-block pins one center AND the arch peak to an axis, moving all deviation to one end, where an indicator is in-place to see it's peak.

The v-block shows the summation of everything. Just read it raw for your peak runout. Forget eccentricity.
When your ammo measures low runout on a v-block, you made straight ammo. Best you can do.
And don't assume that 4thou TIR is 2thou w/resp to a centerline. Your dies and brass springback at varying thickness will set a dynamic centerline and shape (which is often not very round or straight).

 

[Rob L.]

Yes, excellent. That is what I was wanting to know. I do not own that gauge and see how it works by your explanation.
So checking with a V-block is a better way than using this Hornady tool. Great explanation, thanks...

One thing to add is when using the V-block, be sure to use a stop to keep the cartridge in the same place on the V-block while rotating, so as not to read any taper in the case.

 

[QuietTexan]

That's exactly why I got rid of the Hornady gauge and went to 21st Century. V-rollers, case stop, test indicator.

 

[Mikecr]

One thing to add is when using the V-block, be sure to use a stop to keep the cartridge in the same place on the V-block while rotating, so as not to read any taper in the case.

Good point. If the casehead is out of square, that will play havoc with any angled surface measure.
It's also another runout attribute, as it causes cases to chamber bind and throw shots.
Good to keep a mirror handy for quick checks of this. Especially if you just had your lugs lapped..

 

[Mike Matteson]

The one thing is I am very careful on sitting the bullet into the case, and being sure it's straight, and not set on any type of angle. I hadn't use a mandrel at that time. I now have mandrels to do the work with. I am having a problem with a neck reduction. It's a 280AI Peterson case. I am reducing the neck to 6mm with 280AI FL Redding Bushing dies. Set the die up in the press with the bottom of the die touching the case base holder. So I am getting the full length. Changed out the decapper rod to a 25-06 rod. The diameter is to large with the 280 decapping rod by the time the neck is size down to .243. Took off the neck expander too. Set up the bushing to be loss by a 4th to 5th. to allow the neck to line up in the bushing to down size the neck. I am stepping the neck down in 3 steps to change the neck size. Where I am having the problem is I can't get the neck resize to the shoulder at the bottom of the neck. About 1/8" short of the shoulder. The necks all have been cut to length to start with. So that not a problem of different case lengths. The case in the picture hasn't had the neck turn for thickness. It's just a practice case to see what problem I am running into, and that the problem I have. I don't know that the hell I am doing wrong. I can if needed to have a bushing die built to do the work or have a bushing that longer to do the job. Any answers to what I am doing wrong. I figure I am missing something.

 

[QuietTexan]

Where I am having the problem is I can't get the neck resize to the shoulder at the bottom of the neck. About 1/8" short of the shoulder.

6-280 AI? What's the chamber going to be set to for neck thickness? Depending on that you could ream out with an LE Wilson trimmer to solve potential donut issues instead of turning.

I don't think you're doing anything wrong - it looks like the bushing die is working correctly and not sizing the full length of the neck. The benefit of using the bushing die is you can step down, but you can't fully resize the case unless you have an FL die.

Do you have a 6mm neck die? Not a bushing neck die, something like a cheap-o Hornady 46041 fixed 6mm neck only die. Or a FL die for another 6mm that the 280 body will fit inside of and you can back off to just hit the neck? I've heard of guys using WSSM FL dies to finish necked down wildcats because everything fits up into the body, especially in the 223 and 243s.

I also don't see why if the case fits the chamber you couldn't load it and shoot it to set the shoulder, then resize with the 280AI die and smaller bushing going forward. If the thickness isn't a problem every other bushing diel sizes the same way, that part of the neck just doesn't expand as much when you fire.