Necking down questions

[Lucky6547]

Hello,
Interested in a 6x47L. Having never necked down (or up) for a wildcat, I was wondering about various things...If you were to neck turn before sizing down the neck, would you reduce the likelihood of the donut? Or do you not remove enough when such similar calibers are involved?
Would your neck thickness remain the same after neck turning and then sizing to 6mm from 6.5? Or would you need to turn again after sizing?
Any other insights from people with experience would be appreciated.
Thanks,
Ken

 

[bheadboy]

necking down the neck thickness grows, and may not be uniform
necking up the neck thickness thins, and may not be uniform

thus to control the resultant thickness of the neck do the turning after the size change.

Bob

 

[mikecr]

In contrast, I neck turn with cases in new from factory condition.
It's easier to get proper turning mandrel fit, and with the brass well turned, up/down sizing holds in uniformity for me.

Brass will thicken/thin with sizing. So I trial & error to determine original form turn thickness to end up at final thickness after sizing.
Using cases culled anyway, I can usually nail it within a few.

 

[Lucky6547]

This is just a thought experiment for me right now, so let's say you turned the 6.5 virgin brass with a 6.5 turner, and neck down. Wouldn't the new shoulder be less prone to donuts? And even if you needed to turn again, it's already a little more consistent and needs less work after sizing? These are just my conjectures about the process, with no actual hands on experience...it could be that the change from 6.5 to 6 isn't big enough to show any benefit of the extra step...I don't know...

 

[357Mag]

Lucky -

Howdy !

If ( when wildcatting ) you happen to also be doing a " shoulder shove ", you would expect doughnuts fer sher.

For a 6.5 X 47L caliber redux to 6mm, neck wall thickness would thicken.... some.

Story time:
Working on my most recent wildcat project ( a new 6.5mm wildcat ), I thought it would be a great idea to simply start out
w/ .260Rem brass; as it was already 6.5mm. This wildcat includes a fairly modest shoulder shove.
*** One target for the final formed cases, was that they'd be operated w/ .012" neck wall thickness.

As it turned out..... I could not consistently arrive @ .012" neck wall thickness; during outside neck turning the cases.
This was because the 100ea virgin Remington-brand .260Rem cases featured numerous cases that were as-thin-as
.0115" AFTER the shoulder shove. When neck turning, outside of the thinner neck areas would appear as darker brass colour.....
compared to the shinier just-turned portions.

While I'm only talkin' .0005" variance here ( from my best abilities to read such things ), I was taken back a bit by this happening
when starting out w/ the same caliber basic case as what the final wildcat cal was to be.

It then occured to me that use of either 7-08 brass or perhaps .308 brass ( remember THAT stuff ? ) would probably assure
my ability to arrive @ .012" thick final neck thickness for all the cases. As you might imagine, I was not able to come-up w/ either factory 7-08 or .308 brass.

I WAS however, able to obtain all the WIN-brand .358Win brass I wanted.
After forming cases from .358Win, I had some of the new 6.5mm wildcat cases that showed very little materiel removed
( practically brass dust ), while most others showed a long/thin continuous chip being cut from the neck ODs.
And.... 2ea cases still showed low spots on the outside of their necks that were darker in appearance than cut surface' brightness !
This was w/ a shoulder shove being included in the wildcatting process. THAT surprised me !

Using the .358Win wildcatted to 6.5mm and shoulders also shoved downward a bit, my doughnuts only amounted to .001 - .0015"
of additional neck wall thickness @ the choke point. That also surprised me, seeinz how I had squeezed the necks down some
.094"..... again..... along w/ a shoulder relocation.

I still wonder how 7-08 or .308 would work as the parent brass, for the mentioned 6.5mm wildcat. From what all I've seen thus far,
I would not be surprised to again encounter some cases that would mic .0115" un-turned.
The larger question would be.... how thick would any resulting doughnuts be, were I to start-out w/ .7-08 or .308 brass ?

Since its likely I'd still have some cases that were too thin in the neck ( purist thinking ), and.... I'd probably also see some doughnut
formation too; then ( for me ).... there's no point of going w/ anything other than .358Win...... when WIN -brand brass will work just fine for this wildcat/hunting rifle project ?

The point:
" Life is like a box of chocolates ...... "
Forrest Gump


With sincere regards,
357Mag

 

[mikecr]

Lucky6547 donuts don't 'happen'. Beyond inherent to factory forming, we put all brass right where it is, including that at the neck-shoulder junction.
And necking down in itself does not cause donuts.

Think of new cases as they come out of the box. They were formed so that they are thicker at the webs than mouths. This thickness tapers from webs all the way to mouths. So new cases have an inherent donut already, due to brass at the neck-shoulder junction being thicker than the neck area near mouths.
This small existing condition is typically taken out of play by expanding necks and bullet seating so that bullet bearing is not into the neck-shoulder junction.

When you expand necks a cal or two, you may be extending neck length to include thicker shoulder brass, amplifying donuts. So an appropriate action here is to neck turn onto shoulders a bit so that the shoulder brass going into neck area(on up-sizing) will not be thicker.
When you neck down a cal or two, you may be reducing neck length which does not put the original thicker shoulder brass into necks(just the opposite).
So your donut situation remains a matter of your plan. What are you doing with thicker shoulder brass?

This is just initial preps I'm talkin here. What brass you later move into the neck-shoulder area is a matter of your sizing with reloading cycles.

 

[waverly]

My 6-47L is a hunting rifle. No turn neck. Built on a Nesika action, 9 twist Kreiger. I set it up to shoot 90 Scirocco's.

Fired brass measures .272
Loaded measures .269
I figured there would be a slight difference on the brass neck thickness, but there is not really. The 6.5 x 47 brass I used was mostly .013 thick with a few sides maybe just a tad under.013. The necked down brass measures .013 as well. I saw this post and was curious and these were the measurements I came up with.

If you are going to build a tight neck rifle based on the 6-47L, I would turn a little before I necked down. I'm a false shoulder and cream of wheat guy. I necked down only enough to get a crush fit when closing the bolt. I use Win.231 pistol powder powder, cci small primer, cow, and some of the foam(kinda like Styrofoam that the florists use) when I fire form.

Like I said mine is for hunting, and it is throated for the 90 Scirocco's ,and the bullet is seated with the boatail just above the neck shoulder junction. There would be no doughnut problem with the bullet seated that long. If I were building a benchrest gun I'd throat it about .040 shorter, use a .269 or so neck, and I would turn into the neck shoulder junction at some point.

These measurements are from my brass, and could vary lot to lot on the brass. It is blue box Lapua around three years old.

I hope this answers some of your questions, Regards, Waverly