Donuts

[CHROME]

How do you tell if you have donuts? I have looked inside the case mouth where the neck meets the shoulder...I don't see any ring. I cut a case in half and this is what I see. I still cannot feel any indentation there though.?? Do I have the dreaded donut?

 

[22BRGUY]

The way I check is to simply take a fired case and try to seat a bullet in it with my fingers and see if the base of the bullet either stops or gets hard to push in past the neck shoulder junction.

 

[BOBC]

The way I check is to simply take a fired case and try to seat a bullet in it with my fingers and see if the base of the bullet either stops or gets hard to push in past the neck shoulder junction.

Donuts should not be a concern unless you're seating or want to seat pass the donut

 

[CHROME]

....I do seat past the neck shoulder junction.

 

[Mozella]

....I do seat past the neck shoulder junction.

Why? People who claim to know about such things say seating bullets past the neck/shoulder junction is not a good thing.

 

[CHROME]

Because that is where the gun shoots best.

 

[dedogs]

Because that is where the gun shoots best.

More information is needed. What cartridge, bullet, powder etc? How many times re-sized, are necks turned, dies you are using etc? Your picture doesn't seem to show a donut but they can be hard to see when they first start to form. 22BRGUY has the right idea to quickly check a case for donuts. If you suspect donuts you must check them all, not just 4 or 5. dedogs

 

[mikecr]

You could directly measure donut area with a properly setup ball mic. It's simply thicker brass near the neck-shoulder junction. This is inherent to case manufacture, final fired form, and sizing applied.
A donut is not just 'a problem', it could also be no problem,, or even helping a load(ex.30WolfPup).
In other words, reloaders cause donuts to be a problem, or not.

Bullet bearing seating through thicker brass(donut), or not but still through neck-shoulder junction, will have to be managed for consistent results. It's essentially amplifying tension variances, unless reduced with process annealing. Neck turning of new(unfired) brass can mitigate issues with it. Partial length sizing of necks and always running an expander mandrel through them (pre-seating) will help keep the thicker brass out of play.

 

[BOBC]

....I do seat past the neck shoulder junction.

Then I would buy a donut remover. I believe Sinclair sells them.

I had a 7BR several years ago that I seated bullets beyond the donut, but it shot 2- 5shot groups both just slightly under half inch at 200 yds. with no pressure signs. So I did not buy a donut remover. Even though the loaded round case necks showed burnish marks on the outside. But if it concerned me, I would have bought one in a heart beat. Of course my loaded round case necks did not look very nice, but they shot nice little groups.

 

[1lnbrdg]

Powdered or Glazed?

 

[CaptainMal]

All that talk and no-one answered the question. Is that a picture of a "donut" where it bulges out right at the beginning of the neck inside?

I say if you can feel the bulge and scratch on it with a probe where you have it cut open, it is a donut. Now I also say if it bothers you, just take a simple inside cutter sized properly so it is just smaller than the inside of the neck. Then cut it out.

 

[Brians356]

The pic you posted does not suggest any donut. But most cases which have been in use have something of a donut, however insignificant.

I use pin gages to probe inside necks (both just fired, or just sized) and have determined that most if not all unturned case necks are tapered slightly in thickness, being thinner at the case mouth than near the shoulder junction by from .001" to .003". Look at many SAAMI chamber drawings - they indicate the neck portion can and will taper slightly towards the mouth. And the way brass cases are "draw" formed necessarily results in case walls that taper from the web all the way to the case mouth.

Assuming your unturned necks are indeed slightly thicker near the shoulder than at the mouth, if you size them using a cylindrical bushing, the neck ID will be forced to slightly conical. If you then probed the necks with a pin gage that is a slip fit into the case mouth, you typically encounter an obstruction just ahead of the shoulder junction, but it will only be .001" to .002" tighter there than at the case mouth. Is that a "donut"? I don't think so. I think it is a gradual narrowing and perfectly normal after sizing the neck. And if the narrowing there is that slight, seating a bullet past it will not cause a problem in a typical "no-turn" chamber.

I think a real problem donut will be both more pronounced, and more abrupt, than what I described above, and than what I your photo suggests.
-

 

[CHROME]

Just to give you a little bit more information. I turned the brand new Lapua brass to .012 thick. It is 6 x 47 so I started with a 6.5 x 47 case and necked it down to 6 mm using the KM turner. I then size them down and use my expander mandrel to get my desired .002 neck tension. I have shot these approximately 5 times. I anneal them after every two shootings with my Bench source annealer. I have never gone back and returned them since the original turning.

 

[BOBC]

Powdered or Glazed?

NO JELLY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[Brians356]

I started with a 6.5 x 47 case and necked it down to 6 mm using the KM turner.

How do you neck down a case using a KM turner?
-

 

[CHROME]

Wrong wording....sorry. At work....rushing. Neck down with a Redding 6×47 die with a bushing in it. Don't know what size till I get home, but I size down 1 tme, not in steps. The I run the 6 mm expander thru it, then turn it.

 

[dogdude]

CHROME, use a .242 pin gauge, it will tell you if you have a ''donut''. If you do trim all to the EXACT length you want and use your turner to cut a bit into the shoulder and on the next firing that donut blends into the shoulder...no need for jam or jelly!

 

[CHROME]

That's what's strange, I use a 241. Pin gauge and I feel nothing. That is why I went ahead and cut one in half. When I seat the bullet it is not smooth at all. And my groups are starting to open up. I was thinking about using the reamer on the inside to try to get rid of them, but I would like to learn how to not get them in the first place. If that makes sense.

 

[CHROME]

So should I have to retrim the necks after a couple of firings? That is something I have never done before but I am open to it if that is the answer.

 

[CHROME]

So should I have to retrim the necks after a couple of firings? That is something I have never done before but I am open to it if that is the answer.

I just saw on the other post regarding neck turning on fire forming brass. So it sounds like something I will try thank you all for your help and input.