If someone suspects they have or would just like to check whether or not the "dread donut" is there couldn't he turn a steel rod the exact size {minus .0005" or so, just enough so it will go in} of the resized case mouth to use as a checking tool??? If it passes through then no donut, but if it stops at or just before the junction of the neck and shoulder then you got donut??? It seems like this would be a simple enough test or way to positively know if you have donuts or not. I get that owning the lathe is the hard part, but that aside it should be just this simple, correct????
Another "donut" question????
- Thread starter msinc
- Start date
As Rem06 said; use a bullet as a gage, I want my case necks to expand when fired, when firing a new to me rifle I fire the first round then take the next round and place the bullet of the unfired case into the neck of the fired case, I do not want to find the bullet is tight in the case neck of the fired case.
Then there is the .0005” clearance; I would not find that necessary, the outside diameter of 270 case necks is .308”, when checking 30/06 case neck diameter I use the neck of the 270 case. If the primers have not been removed a vacuum is created when the two cases are shoved together.
But if you choose to use the pin type gage the case will have to be sized.
One day someone will make a step type pin gage; it will not be something new, in the old days the step gage was called a go/not go gages.
F. Guffey
Then there is the .0005” clearance; I would not find that necessary, the outside diameter of 270 case necks is .308”, when checking 30/06 case neck diameter I use the neck of the 270 case. If the primers have not been removed a vacuum is created when the two cases are shoved together.
But if you choose to use the pin type gage the case will have to be sized.
One day someone will make a step type pin gage; it will not be something new, in the old days the step gage was called a go/not go gages.
F. Guffey
The flat base bullet into a fired case works nicely. Boat tails may not have the pressure ring which is usu .0005 greater than bullet bearing surface. If it stops at shoulder\neck junction, you have a donut. An established donut can be extremely hard and requires reaming to remove.
Isn't the donut worse, or maybe "more able to be detected" in a sized case using no expander ball??? And/or, wouldn't this be the best time to ream it out, if you could get the proper size reamer????
Can you have donut enough to cause problems and not have it show in a fired expanded case, but then show up after resizing????
Can you have donut enough to cause problems and not have it show in a fired expanded case, but then show up after resizing????
If when sizing the case a sizer plug/neck expander is used there is a chance pulling the sizing plug through the neck can be difficult; after that someone has to decide if pulling the sizing plug/expander through the neck pushes the donut to the outside. And then there are those that pull the shoulder forward when the expander is pulled through the neck.
F. Guffey
The only time a donut causes a problem is when you seat a bullet into or thru it.
Not to disagree at all, maybe it's just my ineptitude showing up, but the problem I had with reaming was concentricity of the reaming process being in harmony with the concentricity of the overall case body itself. I'm sure I was close to being concentric with the case body on most but perfection is hard to determine. On the other hand, maybe it doesn't matter that much if at all.
Guy's a reamer will ream a hole round but if not guided it will ream off center.
Cutting necks is the same . The pilot with neck turning determins the thickness but till the case is fired the neck can be off center to the case .
So cutting a donut out the the case and neck should be held in a die when reaming
Thanks again for all the replies fellas!!! Please don't get me wrong, I understand the consequences of the donut...I get what it causes and I get that it can be a problem to get rid of. i understand it causes problems only when a bullet is seated into it.
I think it is an excellent point that when reaming it out the inside of the case neck can get out of concentricity to the rest of the case.
My main concern is with absolutely, positively, beyond any doubt detecting the donut in a case. It seems like "the dread donut" is a much talked about topic, and rightly so as it can cause problems one might not immediately attribute to having a donut in the case. Not much is ever written about detecting or positively "ID ing" them, yet everyone can tell you what they cause. A metal hook or probe is great for finding a step, but a slight donut might be easily missed as it slides up the ramp and back down lacking a sharp edge to catch on. I am sure donuts in your cases will manifest on a chronograph or target...but so will many other things.
What I am after is a simple easy positive check to incorporate into the reloading steps to know or identify once and for all whether it is there. I thought there might be a time when it was "at it's worst" and therefore most easily able to be detected, i.e. after resizing, before resizing, etc.
I think it is an excellent point that when reaming it out the inside of the case neck can get out of concentricity to the rest of the case.
My main concern is with absolutely, positively, beyond any doubt detecting the donut in a case. It seems like "the dread donut" is a much talked about topic, and rightly so as it can cause problems one might not immediately attribute to having a donut in the case. Not much is ever written about detecting or positively "ID ing" them, yet everyone can tell you what they cause. A metal hook or probe is great for finding a step, but a slight donut might be easily missed as it slides up the ramp and back down lacking a sharp edge to catch on. I am sure donuts in your cases will manifest on a chronograph or target...but so will many other things.
What I am after is a simple easy positive check to incorporate into the reloading steps to know or identify once and for all whether it is there. I thought there might be a time when it was "at it's worst" and therefore most easily able to be detected, i.e. after resizing, before resizing, etc.
OP you are right, a lot of the methods like a paper clip would not work if the donut is slight in nature.
Using anything like a rod or bullet only works on a fired case if your case neck expands after firing exactly so that the internal diameter is the diameter of your rod/bullet. You could get that if you neck turn your case to exact dimensions (to give you consistent neck thickness) and ream your chamber so that it will allow your neck to expand so that after spring back, the ID is the exact diameter of your rod/bullet.
If you use a sized case, the same applies, i.e. you have to have a turned neck case so that the walls are consistent, size it so that the ID is slightly larger than your rod/bullet that you are using as a gauge.
One problem with both of the above is it depends also on a consistent spring back and so the work hardening nature of the case would also need to be controlled. It's partially the same problem as getting consistent neck tension dealing with the part of neck tension that is produced by a consistent neck ID.
Using anything like a rod or bullet only works on a fired case if your case neck expands after firing exactly so that the internal diameter is the diameter of your rod/bullet. You could get that if you neck turn your case to exact dimensions (to give you consistent neck thickness) and ream your chamber so that it will allow your neck to expand so that after spring back, the ID is the exact diameter of your rod/bullet.
If you use a sized case, the same applies, i.e. you have to have a turned neck case so that the walls are consistent, size it so that the ID is slightly larger than your rod/bullet that you are using as a gauge.
One problem with both of the above is it depends also on a consistent spring back and so the work hardening nature of the case would also need to be controlled. It's partially the same problem as getting consistent neck tension dealing with the part of neck tension that is produced by a consistent neck ID.
I ID ream my 300NM brass after firing and cut some brass at the case neck junction with a forster reamer. resize case, load, fire and repeat. If I was truly that worried about it any more, it is time for new brass.
208Amax, 210 Berger and 215 OTM are not a problem but my 230"s are. It works for me.
it is rather easy to get new brass or stay clear of the donot. it is a good idea to know it can be there the tools you may need to detect a minor donot are likely way more expensive than new brass?
It has been like that since R. Lee made Target Model die sets. The top of the die was the guide and the instructions made it clear; do not forget to lube the reamer guide.
F. Guffey
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