Doughnuts inside case neck
- Thread starter josebd
- Start date
Try it and see. Size a case and see if you can feel a bump inside the neck where you'd expect the donut to be. I believe they form better by fireforming.
Donuts are fourm fro the case being stretched Forward And the angel change at the shoulders . When you size the neck you move the metal to the inside That makes the donut on the inside . You can then ream it out or just deal with it . I just deal with mine
I size the brass and don’t use a expander ball and seat the bullet forward of the donut
The reamer I have had enough free bore where I can do it
Expander ball I take off all my dies for that. Reason
If you have a donut and use a expander ball you moving the donut to the outside of the neck and you also pulling the shoulder forward which change head space
I size the brass and don’t use a expander ball and seat the bullet forward of the donut
The reamer I have had enough free bore where I can do it
Expander ball I take off all my dies for that. Reason
If you have a donut and use a expander ball you moving the donut to the outside of the neck and you also pulling the shoulder forward which change head space
Yes. I use the expander ball or a mandrel to help keep the at bay. I think certain calibers suffer them more than others.
Seems like a great idea
The only way to get rid of a donut is to ream it out or expected it out and trimmed it off
I was thinking of the benchrest situation where one turns the neck but stops short of the shoulder. This leaves a "donut" on the outside of the neck which is moved to the inside upon fireforming. The donut acts as a depth stop for those who seat their bullets with finger pressure. I rarely use an expander when sizing cases. I let the seated bullet do that. Seems dumb and unnecessary to size it down and re-expand it.
For what reason is this "donut" a problem? Does it hinder powder gases from exiting the case?
For what reason is this "donut" a problem? Does it hinder powder gases from exiting the case?
I am curious if the caliber or the case design has the most impact. Do the cases with the more narrow shoulder angle which causes brass flow forward have this happen more often? If so that would lead one to believe that the Ackley improved case design would help a lot. I keep seeing this pop up and i which i had a lot more data on how and why the doughnut forms. I think i understand based on what i said above but it is not based on any facts or testing of my own. I also am wondering if the bushing type dies that dont size the entire neck cause this issue, or make a problem that already exists worse.Yes. I use the expander ball or a mandrel to help keep the at bay. I think certain calibers suffer them more than others.
Seems like a great idea
The sharpest shoulder angle has the least amount of brass movement
I cannot say that it doesn’t cause more of a donut
I cannot say that it doesn’t cause more of a donut
I never had them till I got my first Dasher. I think the fire-forming + high pressure of the cartridge contributed. I could drop a bullet in the neck and it would stop on the doughnut. The barrel had stopped shooting and I was wrapped around the axle about why. I went one bushing size down and put the mandrel button back in the dies. I FL sized every piece of that brass, shot it and it started shooting predictably again. I ended up getting 1000+ more rounds out of that barrel.
I will always use that expander now. I don't really see the downside for the type of shooting I do. I know lots of smarter people than me will tell you to not use it the expander, I originally followed that advice. I think you could ream and turn the brass to help remove the excess brass, but I already hate brass prep. Of course this is just my experience and opinion. I think the key is to not get them in the first place. Kinda like herpes. Once you got em, you got em.
I will always use that expander now. I don't really see the downside for the type of shooting I do. I know lots of smarter people than me will tell you to not use it the expander, I originally followed that advice. I think you could ream and turn the brass to help remove the excess brass, but I already hate brass prep. Of course this is just my experience and opinion. I think the key is to not get them in the first place. Kinda like herpes. Once you got em, you got em.
GSPV
A failure to plan is a plan for failure.
In my 284 Shehane, it was like there was a solid shelf inside the neck. I didn’t have enough freebore to stay away from it.
I tried inside neck reaming. It was not successful for me.
I solved my problem by moving the donut to the outside with an expanding mandrel and then outside neck turning again
I’ve spec-Ed my new reamer with enough freebore that the donut should never be an issue.
I tried inside neck reaming. It was not successful for me.
I solved my problem by moving the donut to the outside with an expanding mandrel and then outside neck turning again
I’ve spec-Ed my new reamer with enough freebore that the donut should never be an issue.
NorCalMikie
Gold $$ Contributor
donuts?
think about it this way. we all know the firing and sizing cycle causes our brass neck to grow requiring trimming. where does this brass come from? why from the case shoulder. now that shoulder brass is thicker than the neck brass. when that shoulder brass migrates into the neck it causes donuts. that is why they tell you when you turn necks to cut into that shoulder a bit. what that does is thin that shoulder brass before it becomes neck. why do bushing dies cause donuts more often. well they really don't. it is just that they push the donut to the inside of the neck where they interfere with bullet seating. that donut might not have even been noticed on the outside of the case unless it was thick enough to interfere with chambering.
yes some cartridges are more prone to donuts. its the angle of the shoulder and how hot you load them. a good indication is how often you have to trim. a good fitting die that doesn't size more than necessary can help.a lot. i find some of the ackley improved cartridges i have never need trimming for the life of the case. No donuts either.
best way to get rid of them. move to the outside with an expander die and turn the necks
think about it this way. we all know the firing and sizing cycle causes our brass neck to grow requiring trimming. where does this brass come from? why from the case shoulder. now that shoulder brass is thicker than the neck brass. when that shoulder brass migrates into the neck it causes donuts. that is why they tell you when you turn necks to cut into that shoulder a bit. what that does is thin that shoulder brass before it becomes neck. why do bushing dies cause donuts more often. well they really don't. it is just that they push the donut to the inside of the neck where they interfere with bullet seating. that donut might not have even been noticed on the outside of the case unless it was thick enough to interfere with chambering.
yes some cartridges are more prone to donuts. its the angle of the shoulder and how hot you load them. a good indication is how often you have to trim. a good fitting die that doesn't size more than necessary can help.a lot. i find some of the ackley improved cartridges i have never need trimming for the life of the case. No donuts either.
best way to get rid of them. move to the outside with an expander die and turn the necks
Frankly, I've never paid much attention to them. I've done .6.5-06 and 6.5-06 AI from .270 Win and .280 Rem cases. What is the giveaway clue/s that they are an issue?
Yo will stat having had bolt lift an extraction
But normally first thing you can see is a ring where the shoulder and the neck join
But normally first thing you can see is a ring where the shoulder and the neck join
GSPV
A failure to plan is a plan for failure.
My experience with the donut is that it raises its head principally in cartridges that are formed by necking up the parent cartridge.
Some of the thicker brass of the shoulder becomes neck and there is thicker shoulder brass right there to flow up and become neck...too thick neck.
Don’t trust. Verify. In a cartridge like I describe, try neck turning just a hair at a time. Not even touching the upper neck at first. See if the turning doesn’t start biting at the base.
Continue this, after you have neck turned, shoot the case for a good part of its life and then run it over the mandrel and through the neck turner, still on its final setting from the original case prep. See if it doesn’t clean up brass at the base of the neck.
It did for me.
Some of the thicker brass of the shoulder becomes neck and there is thicker shoulder brass right there to flow up and become neck...too thick neck.
Don’t trust. Verify. In a cartridge like I describe, try neck turning just a hair at a time. Not even touching the upper neck at first. See if the turning doesn’t start biting at the base.
Continue this, after you have neck turned, shoot the case for a good part of its life and then run it over the mandrel and through the neck turner, still on its final setting from the original case prep. See if it doesn’t clean up brass at the base of the neck.
It did for me.
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It can't change the head space. It may, or may not, change the case head-to-datum measurement, though.
That is a fact
So minimizing shoulder bump to the least amount will help you prolong the development? Feels like whe should have threads talking about all the ways and reasons to minimise working the brass.
you are.right. flow is a.bad.word to use to describe it. but to quote guffey you can't actually push the shoulder back either.
what actually happens is this
we will start with a loaded round in the chamber. now that case is slightly shorter than the chamber we strive for 1 to 2 thousands. when fired at the case body/shoulder junction part of that shoulder becomes case wall. at the neck/shoulder junction part of that shoulder becomes neck. fireforming on a very small scale
now when you resize that case the events are reversed. at the case body/shoulder junction a small piece of case wall becomes shoulder. at the shoulder/neck junction a small piece of neck becomes shoulder.
over several cycles that shoulder brass migrates into the neck. you have to realize for just a moment at firing that brass is plastic the only direction it can move is towards the neck. that is why you have to trim.
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