I have ran into some doughnuts on some necked down 270 WSM brass to 6.5 WSM brass. I use Redding bushing dies. Would using a .002-.003 smaller bushing than i am already using, then "push" the doughnut to the outside with an expander mandrel work? I already tried purchasing a Foster trimmer and inside neck reaming tool. Issue is that the tight neck chamber doesn't allow the neck to open up enough to only cut the doughnut. Looking for a way to figure this out for future projects....
Expander mandrel and doughnuts
- Thread starter rhovee
- Start date
Dusty Stevens
Shiner
The donut is best left alone. Its not hurting anything and when you try to cut it out you get broke off necks- that shuts you down in your tracks. As long as your freebore is correct you have nothing to worry about. If you have donuts before you ever shoot them just from necking down just run your expander in there right before you turn your necks and turn em normal.
Lapua40X
California Hunter Education Instructor
Reddng disagrees with you. From their web site: http://www.redding-reloading.com/tech-line-a-tips-faqs/147-advanced-case-forming-operations-
"The "Donut"
The second consideration is the formation of a "donut". This is a ring of thicker brass inside the neck of the newly formed case. The donut appears when the neck-shoulder junction of the newly formed case ends up closer to the base than the parent cartridge. This donut must be removed or dangerous pressures will result due to the lack of clearance for the case neck to release the bullet. Again, we recommend a minimum clearance of 0.003"."
Dusty Stevens
Shiner
Like i said if you have the correct freebore it matters none. If youre shoving the bullet in past the neck then yes neck clearance may cause an issue.
Size 6.5 WSM brass in a standard fl die. Expand. Outside neck turn to shoulder.
My 243 bushing doesnt size all the way to the shoulder. It looks like a donut, but is not one.
Dusty Stevens
Shiner
get your barrel throated longer
6MMsteve
Gold $$ Contributor
what he said or use a collet die, trim your necks before you resize, and anneal them, I think
Dusty Stevens
Shiner
turkey pot pies.
They say .003" clearance from case neck to chamber is needed.
Does that refer to diameter difference?
Or is that the clearance all the way around the case neck requiring a .006" diameter difference?
It's interesting as their full bushing dies size case necks several thousandths short of case shoulders creating an external donut at that juncture. No chamber necks I know of are relieved there so internal donuts won't be formed as case necks may expand to chamber neck limits.
Redding claims that external donut centers case necks in chamber necks in spite of it being smaller diameter than chamber necks.
If you have problem with Redding why don't you e-mail them instead of trying to play expert.
I know some don’t like reviving old threads, but this one addresses My current concerns and can save a lot of time instead of starting over.
I just started into 6BRA, turned necks, and am experiencing My first donuts. Sized with a bushing, finished off with a mandrel, loaded up and went to a match. The rounds chambered very hard. I finally figured out I had donuts, I had pushed them to the outside, and caused the tight Chambering problem.
Donuts are not a problem if We don’t load past them. I know they can be removed by inside boring, or cutting the outside neck down into the shoulder before fire forming. IN MY MIND, THIS WEAKENS THE CASE.
At the same match I witnessed a catastrophic failure where a high end BR rifle exploded. The reason has not been determined. All of the obvious causes have been eliminated. The best theory was a jacket separated, stayed in the bore, and the next round went boom. I’m wondering If a case neck could have separated, stayed in the bore, causing the explosion?
Now that I know I have donuts, I think I can solve My problem by not running the mandrel past the donut, and not seating the bullet below it. Both of which I can do.
All thoughts welcome please.
I just started into 6BRA, turned necks, and am experiencing My first donuts. Sized with a bushing, finished off with a mandrel, loaded up and went to a match. The rounds chambered very hard. I finally figured out I had donuts, I had pushed them to the outside, and caused the tight Chambering problem.
Donuts are not a problem if We don’t load past them. I know they can be removed by inside boring, or cutting the outside neck down into the shoulder before fire forming. IN MY MIND, THIS WEAKENS THE CASE.
At the same match I witnessed a catastrophic failure where a high end BR rifle exploded. The reason has not been determined. All of the obvious causes have been eliminated. The best theory was a jacket separated, stayed in the bore, and the next round went boom. I’m wondering If a case neck could have separated, stayed in the bore, causing the explosion?
Now that I know I have donuts, I think I can solve My problem by not running the mandrel past the donut, and not seating the bullet below it. Both of which I can do.
All thoughts welcome please.
You're right, but it would be better still to not create problem donuts.
Are you heavily FL sizing?
What if you shoulder bump after neck sizing(including expansion)?
The donut is formed by upward brass flow into the case neck during sizing. The amount of upward brass flow depends on how much the case body diameter is reduced. Meaning how fast does your OAL increase with each sizing.
And if a expander is used with a full length non-bushing die and the necks are skim turned the donut is removed. And its simple, do not neck turn cases that were sized with a bushing die that does not size all of the neck.
Brass Preparation
Before we go any further, size your brass with a full-length non-bushing die and trim to uniform length. Both these tasks are VERY important. If the brass is new, run it over the expander and trim to uniform length. While I don’t like non-bushing dies for regular case sizing, this is where they are important. For neck-turning, you have to size the neck all the way to the shoulder junction and a bushing die always leaves about 0.050″ unsized (by design, you can’t fix that). If all you have are bushing dies, I recommend the Hornady New Dimension as your non-bushing die, they are well made and leave the brass very concentric.
And if a expander is used with a full length non-bushing die and the necks are skim turned the donut is removed. And its simple, do not neck turn cases that were sized with a bushing die that does not size all of the neck.
Neck-Turning Basics
https://www.accurateshooter.com/technical-articles/neck-turning-basicsBrass Preparation
Before we go any further, size your brass with a full-length non-bushing die and trim to uniform length. Both these tasks are VERY important. If the brass is new, run it over the expander and trim to uniform length. While I don’t like non-bushing dies for regular case sizing, this is where they are important. For neck-turning, you have to size the neck all the way to the shoulder junction and a bushing die always leaves about 0.050″ unsized (by design, you can’t fix that). If all you have are bushing dies, I recommend the Hornady New Dimension as your non-bushing die, they are well made and leave the brass very concentric.
RegionRat
Gold $$ Contributor
@Rat Rifle if that BR rifle blew up due to a case neck obstruction followed by another shot... I have to wonder how the operator didn’t notice the missing neck when the case was extracted. I realize some folks hammer rounds downrange quickly to catch a condition before it changes, but then I also think it should have been easy enough to collect the evidence and find a case with a missing neck?
Back to your donut... I read where you were sizing with a bushing die and expander mandrel, but in Uncle Ed’s post there is an important concept with regard to the subtleties in the sizer used for neck turning. The devil is in the details down at the shoulder-neck junction where the donut will form in terms of the sizer that is used to prep for neck turning. Also, the dressing and design of the turning tool needs some study to avoid over or under removing material there.
Many times we have discussed bushing details where in one direction there may be a large chamfer and in the other it is more sharp. I’m still in the camp of having a carefully selected FL die, with a diameter that suits my turning pilot. I don’t turn much, but when I used to have to make a silk purse out of a sow‘s ear so to speak, the challenge to working with brass back in the bad old days was you never knew what the batch thickness was going to start with, and how bad the initial runout was. A FL sizer does hit far enough down the neck, but due to runout and variable neck thickness, I still used mandrels to get the ID to play well with the turning pilot.
I did whatever it took to avoid reaming. That is because reaming was a PIA that took practice and experimentation to perfect. As a result, I am always reluctant to take on wildcats that mean I have to start with marginal brass and neck down.
For fun, take a look at the videos of the IDOD neck turning machines with respect to how tools can blend the neck-shoulder. That machine simultaneously cuts the bore, so no need to follow up with a reamer. It is a thing of beauty to watch.
https://fclassproducts.com/the-idod-case-turner
Back to your donut... I read where you were sizing with a bushing die and expander mandrel, but in Uncle Ed’s post there is an important concept with regard to the subtleties in the sizer used for neck turning. The devil is in the details down at the shoulder-neck junction where the donut will form in terms of the sizer that is used to prep for neck turning. Also, the dressing and design of the turning tool needs some study to avoid over or under removing material there.
Many times we have discussed bushing details where in one direction there may be a large chamfer and in the other it is more sharp. I’m still in the camp of having a carefully selected FL die, with a diameter that suits my turning pilot. I don’t turn much, but when I used to have to make a silk purse out of a sow‘s ear so to speak, the challenge to working with brass back in the bad old days was you never knew what the batch thickness was going to start with, and how bad the initial runout was. A FL sizer does hit far enough down the neck, but due to runout and variable neck thickness, I still used mandrels to get the ID to play well with the turning pilot.
I did whatever it took to avoid reaming. That is because reaming was a PIA that took practice and experimentation to perfect. As a result, I am always reluctant to take on wildcats that mean I have to start with marginal brass and neck down.
For fun, take a look at the videos of the IDOD neck turning machines with respect to how tools can blend the neck-shoulder. That machine simultaneously cuts the bore, so no need to follow up with a reamer. It is a thing of beauty to watch.
https://fclassproducts.com/the-idod-case-turner
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