Case Neck Doughnut Question

[Bill2905]

If one repeatedly sizes a bottleneck case with a bushing die, is it inevitable that the case will develop a thickened region (the doughnut) at the junction of the shoulder and the neck? Or, is this a function of multiple variables? In my situation, I am sizing Lapua 6BR cases with a Redding Type S bushing die and shooting fairly mild loads.

[bigedp51]

There is a small section of a bushing die that does not touch the base of the neck as shown in the image below. When you neck turn the shoulder area is thicker and can flow upward into the neck. So this thicker upward brass movement flows into the unsized are in the photo below and is less of a problem. If and when a donut becomes a problem you use a standard full length die and the expander will push the donut to the outside of the neck and you turn the neck again.

https://i.imgur.com/O5m9mBL.jpg

http://www.mssblog.com/wp-content/uploads/2016/01/sizing_line.jpg

http://www.mssblog.com/wp-content/uploads/2016/01/sizing_line.jpg

[mikeinco]

why are you concerned ?
most of my bullet are only in the neck(6br, 6 dasher, 30 br).


If one repeatedly sizes a bottleneck case with a bushing die, is it inevitable that the case will develop a thickened region (the doughnut) at the junction of the shoulder and the neck? Or, is this a function of multiple variables? In my situation, I am sizing Lapua 6BR cases with a Redding Type S bushing die and shooting fairly mild loads.

[Robinhood]

why are you concerned ?
most of my bullet are only in the neck(6br, 6 dasher, 30 br).


Maybe he has a different cartridge and he seats his bullets to the bottom of the neck? Maybe?

[Fuj']

why are you concerned ?
most of my bullet are only in the neck(6br, 6 dasher, 30 br).

"Most" is your key word here. What bullet do you seat below the donut
region ??

There was mention of using an expander to push the donut to the outside
then turn the neck, and most will do that, however, I prefer to leave the
outside neck alone. After fired several times, I check for any donut being
formed and ream that area with an under sized I.D. stub reamer. Normally
my pin gages will give me an early heads up.

[charlie b]

If the doughnut builds don't you end up headspacing off the doughnut instead of the neck? Just curious.

[Nor Cal Mikie]

Why would you end up "head spacing" when reloading? Already got the chamber and are reloading for THAT chamber?
Consider going to a shorter BT bullet that won't reach the donut. And if the donut is causing a problem, use a mandrel, push it to the outside and turn it off. Whatever you do with that donut will weaken the case so avoid it as much as possible.

[mikeinco]

he clearly says 6br
"I am sizing Lapua 6BR cases with a Redding Type S bushing die"


Maybe he has a different cartridge and he seats his bullets to the bottom of the neck? Maybe?

[mikeinco]

ok i lied.......ALL oh my


"Most" is your key word here. What bullet do you seat below the donut
region ??

There was mention of using an expander to push the donut to the outside
then turn the neck, and most will do that, however, I prefer to leave the
outside neck alone. After fired several times, I check for any donut being
formed and ream that area with an under sized I.D. stub reamer. Normally
my pin gages will give me an early heads up.

[mikeinco]

general questions get general answers...
ask a specific question with specific details

[charlie b]

Why would you end up "head spacing" when reloading? Already got the chamber and are reloading for THAT chamber?
Consider going to a shorter BT bullet that won't reach the donut. And if the donut is causing a problem, use a mandrel, push it to the outside and turn it off. Whatever you do with that donut will weaken the case so avoid it as much as possible.

If the donut is external (which it seems to me it would be) the case will enter the chamber and then stop when the donut meets the neck in the chamber, leaving a bit of space between the chamber and the shoulder of the cartridge. Or is the donut small enough to enter the neck area?

[Bill2905]

why are you concerned ?
most of my bullet are only in the neck(6br, 6 dasher, 30 br).

I'll rephrase the question. Is thickening at the neck/shoulder junction very likely to occur or is this difficult to predict?

Why do I ask? I have been experimenting with a bushing die and became aware of the potential for brass thickening at the neck/shoulder junction when using this type of die. I had my 6 BR barrel throat cut so that the base of the bullets I want to shoot will rest near the bottom of the neck when seating them 0-20 thousandths off the lands. Knowing this, I expect that brass thickening may become something that has to be dealt with because of where I seat the bullets. The remedies include neck turning, reaming, etc., all things that I don't really want to get into. Maybe some day but, not now. So, if all that is in my future, I may ditch the bushing die and go another route.

[bigedp51]

Bushing dies work best with neck turned brass in tight neck chambers. And the Redding bushing dies come with a expander for a reason, for those who do not neck turn.

There is also a reason why so many reloaders use a body die and a Lee collet die rather than a bushing die. And the main reason is less neck runout with the Lee collet die.

I have Redding bushing dies, Lee collet dies and prefer Forster full length dies in my factory rifles with larger SAAMI chambers.


Tech Line & Tips (FAQs)
https://www.redding-reloading.com/tech-line-a-tips-faqs/140-bushing-selection (https://www.redding-reloading.com/tech-line-a-tips-faqs/140-bushing-selection)

Bushing Selection
If the neck wall thickness varies more than 0.002", it may be necessary to use a bushing a couple of thousandths smaller than your calculations indicate, and then use a size button in the die to determine the final inside neck diameter.

The bushing floats, and can move from side to side and even tilt inside the die. And the more your case necks expand when fired the greater chance of inducing neck runout.

Tech Line & Tips (FAQs)
https://www.redding-reloading.com/tech-line-a-tips-faqs/142-concentricity-a-bushing-dies (https://www.redding-reloading.com/tech-line-a-tips-faqs/142-concentricity-a-bushing-dies)

Concentricity & Bushing Dies
From tests we have conducted, we have learned that selecting the correct bushing is the most important factor in producing sized case necks that have good concentricity with the case body. Our tests showed that case neck concentricity is directly proportional to bushing size. In other words, as you size case necks with progressively smaller bushings, the concentricity gets progressively worse.

Tech Line & Tips (FAQs)
https://www.redding-reloading.com/tech-line-a-tips-faqs/146-concentricity-problems (https://www.redding-reloading.com/tech-line-a-tips-faqs/146-concentricity-problems)

Concentricity Problems
a.k.a Neck Runout With Bottleneck Cases

We have conducted many tests over the years on the various factors contributing to concentricity problems with bottleneck cases. We have repeatedly found a definite correlation between the uniformity of the brass (or lack of it) and the resulting concentricity of the neck to the body of the case.

An interesting experiment also revealed that neck turning of brass that was intentionally sorted as non-uniform, showed little or no concentricity improvement when used in standard S.A.A.M.I. spec chambers. Conversely brass that was sorted and selected for uniformity remained uniform and concentric with or without a neck turning operation.

Bottom line, since you said you do not want to neck turn, you will need to buy high quality brass with uniform neck and body thickness. "BUT" the Redding bushing die FAQ also tells you that you may have to size the neck in several progressive smaller steps to keep from inducing neck runout in larger SAAMI chambers. So again bushing dies work best with neck turned brass in custom tight neck chambers. Meaning in chambers that do not allow the neck to expand as much as factory SAAMI chambers. And at the Whidden custom die website they tell you with non-bushing full length dies they get better case concentricity than with bushing dies.

[Bill2905]

Bushing dies work best with neck turned brass in tight neck chambers. And the Redding bushing dies come with a expander for a reason, for those who do not neck turn.

There is also a reason why so many reloaders use a body die and a Lee collet die rather than a bushing die. And the main reason is less neck runout with the Lee collet die.

I have Redding bushing dies, Lee collet dies and prefer Forster full length dies in my factory rifles with larger SAAMI chambers.


I specified a no-turn neck so I assume my chamber is cut to SAAMI specs. Good info, thank you.

[243winxb]

No donut in 243 Win. using Redding type S fl bushing die. 20 plus loadings of Win brass, neck turned.

Using Rem brass for my other 243 gun, unturned brass, bushing die. No donut.

[Bill2905]

No donut in 243 Win. using Redding type S fl bushing die. 20 plus loadings of Win brass, neck turned.

Using Rem brass for my other 243 gun, unturned brass, bushing die. No donut.

Do you size your 243 cases with or without the expander?

[Steeltrap]

When I shot a lot of long distance with my 6.5x55 cartridge, I would get the "doughnut" on the inside of the case neck right at the bottom. Forster had the answer to remove the brass: https://www.eabco.net/Forster-Case-Neck-Reamers_p_13984.html

https://media.mwstatic.com/product-images/src/Primary/590/590193.jpg?imwidth=2200

[243winxb]

Do you size your 243 cases with or without the expander?

Turned neck , no expander. Unturned necks, the expander may be used. lube inside of case neck. But do test both ways with unturned brass. With and without the expander. Has a lot to do with the brass. Some neck wall thickness are better then others.