The Dreaded Donut What is the Cause?
- Thread starter kwak
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Re: The Dreaded Donut What is the Cause?
I don't know that this is the only cause, but it also happened to me when necking up Lapua .243 Brass to .260. Seems that when necking up, the thicker brass in the shoulder region is pulled into the neck/shoulder junction of the larger necked case, creating the donut. I believe the potential exist for excessive pressures due to the neck being too thick in the donut area to expand and release the bullet cleanly. Additionally, with inconsistent neck tension along the length of the neck, it couldn't be good for accuracy.
When necking down 7mm-08 brass to .260, I experienced no problems.
John
I don't know that this is the only cause, but it also happened to me when necking up Lapua .243 Brass to .260. Seems that when necking up, the thicker brass in the shoulder region is pulled into the neck/shoulder junction of the larger necked case, creating the donut. I believe the potential exist for excessive pressures due to the neck being too thick in the donut area to expand and release the bullet cleanly. Additionally, with inconsistent neck tension along the length of the neck, it couldn't be good for accuracy.
When necking down 7mm-08 brass to .260, I experienced no problems.
John
Re: The Dreaded Donut What is the Cause?
Yup, necking up 22-250 to 6MM. I do the expansion, then lightly turn the neck into the shoulder, removing the donut from the outside.
Yup, necking up 22-250 to 6MM. I do the expansion, then lightly turn the neck into the shoulder, removing the donut from the outside.
M
milo 2.0
Guest
Re: The Dreaded Donut What is the Cause?
Just last night I was loading some 6.5x47, and noticed the donut on a few twice fired cases. I'm not necking up or down, has me baffled.
Only thing I can think of is not neck sizing the whole length of the neck, and oversize neck in the chamber.
I know I'm not buying a neck turner, and if it keeps up, the barrel is gone too!
Just last night I was loading some 6.5x47, and noticed the donut on a few twice fired cases. I'm not necking up or down, has me baffled.
Only thing I can think of is not neck sizing the whole length of the neck, and oversize neck in the chamber.
I know I'm not buying a neck turner, and if it keeps up, the barrel is gone too!
Re: The Dreaded Donut What is the Cause?
I don't known that I've ever seen this donut. Heard of it but anyone have a pic to share. I want it know if i ever see it on my brass.
I don't known that I've ever seen this donut. Heard of it but anyone have a pic to share. I want it know if i ever see it on my brass.
Re: The Dreaded Donut What is the Cause?
Norma 6mmXC brass. Loaded 4-5 times. Turned the necks. Full length neck size each loading. Donuts that restrict me from using DTAC's because of their length. They cause a heavier than normal bolt lift without any other signs of over pressure. I am going to try the neck turn expander and see if that gets rid of them. And if it does I might have to do this every 2-3 loads.
But I still don't understand what the cause is.
Norma 6mmXC brass. Loaded 4-5 times. Turned the necks. Full length neck size each loading. Donuts that restrict me from using DTAC's because of their length. They cause a heavier than normal bolt lift without any other signs of over pressure. I am going to try the neck turn expander and see if that gets rid of them. And if it does I might have to do this every 2-3 loads.
But I still don't understand what the cause is.
Re: The Dreaded Donut What is the Cause?
It's my understanding that the donut is formed on the inside of the case neck and that, therefore, turning the neck is not the solution. I believe K&M (and perhaps others) sells a cutting mandrel that removes the donut from the inside.
Here are links to a bit more information:
https://www.kmshooting.com/catalog/neck-...ting-pilot.html
http://benchrest.com/archive/index.php/t-51858.html
This one has some pictures of the donut:
http://home.comcast.net/~jesse99/doughnuts.html
Richard
It's my understanding that the donut is formed on the inside of the case neck and that, therefore, turning the neck is not the solution. I believe K&M (and perhaps others) sells a cutting mandrel that removes the donut from the inside.
Here are links to a bit more information:
https://www.kmshooting.com/catalog/neck-...ting-pilot.html
http://benchrest.com/archive/index.php/t-51858.html
This one has some pictures of the donut:
http://home.comcast.net/~jesse99/doughnuts.html
Richard
Re: The Dreaded Donut What is the Cause?
Ok, the physics of the situation:
There is more brass per unit radius in the shoulder than in the neck. Therefore as the shoulder is pushed up into the neck region by firing and by resizing the thickness of the botton of the neck increases.
So the doughnut is caused by the shoulder brass being squeezed into the neck area.
One can cut it off with a reamer,
one can trimm it off with a trimmer,
one can ignore the problem,
one can retire the case.
These are the options.
Sometimes the choice is based on the length of the shank of the bullet and the position of the dreaded doughnut. no interference == no problem....interference == bad problem.
Ok, the physics of the situation:
There is more brass per unit radius in the shoulder than in the neck. Therefore as the shoulder is pushed up into the neck region by firing and by resizing the thickness of the botton of the neck increases.
So the doughnut is caused by the shoulder brass being squeezed into the neck area.
One can cut it off with a reamer,
one can trimm it off with a trimmer,
one can ignore the problem,
one can retire the case.
These are the options.
Sometimes the choice is based on the length of the shank of the bullet and the position of the dreaded doughnut. no interference == no problem....interference == bad problem.
Re: The Dreaded Donut What is the Cause?
Hi All, well designed modern cartridges such as the 6XC, 6PPC USA, et al (I shoot both) are throated so that even in a new chamber the parallel shank of the bullet does not extend beyond the neck / shoulder junction and the ogive is close to/on/just in the lands. So the problem is circumvented in the first instance. It would be worth gauging your chamber if possible with the Stoney point case gauge or similar and select a bullet that the parallel shank does not extend down that far. Develop a cartridge with a COAL and load that suits your rifle and avoid any issues this way. I haven’t tried the internal neck reamer to remove any donut but I would guess that you could spend a lot of time on this and ruin a lot of cases.
Hi All, well designed modern cartridges such as the 6XC, 6PPC USA, et al (I shoot both) are throated so that even in a new chamber the parallel shank of the bullet does not extend beyond the neck / shoulder junction and the ogive is close to/on/just in the lands. So the problem is circumvented in the first instance. It would be worth gauging your chamber if possible with the Stoney point case gauge or similar and select a bullet that the parallel shank does not extend down that far. Develop a cartridge with a COAL and load that suits your rifle and avoid any issues this way. I haven’t tried the internal neck reamer to remove any donut but I would guess that you could spend a lot of time on this and ruin a lot of cases.
Re: The Dreaded Donut What is the Cause?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kwak</div><div class="ubbcode-body">Where does this thing come from and does it have any effect on accuracy? </div></div>
Causes:
- Necking up cases, makes some of the shoulder become part of the neck.
- Sizing with a bushing die. There is a thin area between the body die and the bushing die that is not supported. Brass eventually gets pushed into this area creating the donut.
Effect:
- Inconsistent neck tension and excessive bullet seating pressure.
- Could inhibit clean bullet release, depending on neck clearance, and spike pressures.
Fix:
- Inside neck reamer
- Always try and neck down, instead of up.
- Use non-bushing FL sizing die.
- Do not seat bullets into the donut.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kwak</div><div class="ubbcode-body">Where does this thing come from and does it have any effect on accuracy? </div></div>
Causes:
- Necking up cases, makes some of the shoulder become part of the neck.
- Sizing with a bushing die. There is a thin area between the body die and the bushing die that is not supported. Brass eventually gets pushed into this area creating the donut.
Effect:
- Inconsistent neck tension and excessive bullet seating pressure.
- Could inhibit clean bullet release, depending on neck clearance, and spike pressures.
Fix:
- Inside neck reamer
- Always try and neck down, instead of up.
- Use non-bushing FL sizing die.
- Do not seat bullets into the donut.
