School me on "the doughnut "

[WeiserBucks]

Fairly new to handloading, I keep hearing people on various forums referencing the doughnut, what is it and why should I consider it's importance?

 

[rcoody]

Fairly new to handloading, I keep hearing people on various forums referencing the doughnut, what is it and why should I consider it's importance?

Well if you use . bushing dies for neck sizing you will experience it

If you use full length sizing dies.you won't

Bushing dies only size part of the neck. The rest of the neck stays at its expanded size. Brass also flows under pressure and migrates from the shoulder into the donut area.

 

[Predator 22]

You can also get it from necking up and down brass. Here is a little info on it.
260 Ackley Case Forming

 

[J E Custom]

Fairly new to handloading, I keep hearing people on various forums referencing the doughnut, what is it and why should I consider it's importance?

Most people that talk about using a doughnut are referring to one method of head spacing a cartridge for fire forming in a larger chamber.

I prefer to use The doughnut method, instead of using the bullet to head space. It is a really good way to save one firing of the brass to reshape it in a larger chamber and not worry about pressure and the case moving forward and stretching the case web.

It is a simple process of sizing only enough of the neck to properly head space the cartridge. this leaves a small doughnut at the base of the neck that head spaces the cartridge correctly.

When neck sizing a case with dies, there is a very small doughnut /ring left if the die is not set to size the hole neck but it does not serve any purpose other than to control the amount of tension on the bullet and because it does not control head space.

J E CUSTOM

 

[rcoody]

Most people that talk about using a doughnut are referring to one method of head spacing a cartridge for fire forming in a larger chamber.

I prefer to use The doughnut method, instead of using the bullet to head space. It is a really good way to save one firing of the brass to reshape it in a larger chamber and not worry about pressure and the case moving forward and stretching the case web.

It is a simple process of sizing only enough of the neck to properly head space the cartridge. this leaves a small doughnut at the base of the neck that head spaces the cartridge correctly.

When neck sizing a case with dies, there is a very small doughnut /ring left if the die is not set to size the hole neck but it does not serve any purpose other than to control the amount of tension on the bullet and because it does not control head space.

J E CUSTOM

That is.the method I use to fireform 6mmar from grendel. It forms a false.shoulder and works.very well.

 

[Mikecr]

Well if you use . bushing dies for neck sizing you will experience it
If you use full length sizing dies.you won't
Bushing dies only size part of the neck. The rest of the neck stays at its expanded size. Brass also flows under pressure and migrates from the shoulder into the donut area.

Rubbish..
The unsized portion of a partially sized neck is not a 'donut'. It is merely unsized area.
Brass also does not 'migrate' into donut area. It is put there with neck upsizing and with heavy sizing of high body taper/low shoulder angle cases. This rolling, thick toward thin, is what you trim away when you cause it -through sizing (not all of us do).

OP, new brass varies in thickness inherent to it's manufacture, tapering from thickest at the webs, and thinning all the way to case mouths. So all brass comes with donut area in necks, as they are thicker nearest the neck-shoulder junction. Some of us turn necks to desired thickness which can remove and mitigate future donuts where done correctly. When we turn, we do so full length of necks and slightly up onto shoulders. This, because once the shoulder and neck expand on first firing, some of the shoulder becomes new neck area. That shoulder brass would have continued in thickness taper, so it would have been thicker, recreating a donut.
Anyway, donut area is only an issue when we make it so. Seating bullet bearing into it is a common problem for tension(bullet grip) and sometimes chamber fit. FL sizing of necks brings thicker donut brass into neck tension, regardless of seated bearing.
So the best way to avoid donuts as a 'problem' is to avoid seating bullet bearing near neck-shoulder junction, and to partially neck size -with bushings.

 

[rcoody]

Rubbish..
The unsized portion of a partially sized neck is not a 'donut'. It is merely unsized area.
Brass also does not 'migrate' into donut area. It is put there with neck upsizing and with heavy sizing of high body taper/low shoulder angle cases. This rolling, thick toward thin, is what you trim away when you cause it -through sizing (not all of us do).

OP, new brass varies in thickness inherent to it's manufacture, tapering from thickest at the webs, and thinning all the way to case mouths. So all brass comes with donut area in necks, as they are thicker nearest the neck-shoulder junction. Some of us turn necks to desired thickness which can remove and mitigate future donuts where done correctly. When we turn, we do so full length of necks and slightly up onto shoulders. This, because once the shoulder and neck expand on first firing, some of the shoulder becomes new neck area. That shoulder brass would have continued in thickness taper, so it would have been thicker, recreating a donut.
Anyway, donut area is only an issue when we make it so. Seating bullet bearing into it is a common problem for tension(bullet grip) and sometimes chamber fit. FL sizing of necks brings thicker donut brass into neck tension, regardless of seated bearing.
So the best way to avoid donuts as a 'problem' is to avoid seating bullet bearing near neck-shoulder junction, and to partially neck size -with bushings.

Opinions.Vary

 

[WeiserBucks]

Good information guys , keep it coming. I'm trying to learn all I can .

 

[Mikecr]

You're confusing donut with false shoulder. Nothing to do with each other..
Go back to my post and learn about what a donut is.

 

[rcoody]

You're confusing donut with false shoulder. Nothing to do with each other..
Go back to my post and learn about what a donut is.

Here is a beautiful picture of a donut used as a.false shoulder to form 6mm AR from 6.5 grendel brass

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[Mikecr]

Your picture does not show a donut,, it's not what a donut 'looks like'.
Whether used as a false shoulder or not, you're showing no more than a partial sized neck.

A false shoulder is not a donut. It's an expanded neck area used for headspacing.
Where needed, we create false shoulders regardless of any actual donut area.
With exception of a seating shelf, purpose built by relatively few short range BR competitors, dounts are not something purposely added, or desired.

This is what a donut looks like. It's subtle, hard to measure, but it can stop a bullet from falling into a case. Most people couldn't care less about it, because it doesn't affect them. Others bring it into problem.

 

[rcoody]

Your picture does not show a donut,, it's not what a donut 'looks like'.
Whether used as a false shoulder or not, you're showing no more than a partial sized neck.

A false shoulder is not a donut. It's an expanded neck area used for headspacing.
Where needed, we create false shoulders regardless of any actual donut area.
With exception of a seating shelf, purpose built by relatively few short range BR competitors, dounts are not something purposely added, or desired.

This is what a donut looks like. It's subtle, hard to measure, but it can stop a bullet from falling into a case. Most people couldn't care less about it, because it doesn't affect them. Others bring it into problem.

In Yor pic I suspect the donut is on the inside of the neck. Run an expandrel mandrel in that neck and push it to the outside and take another pic

 

[J E Custom]

What "I" call a doughnut for example, is when I size a 375 rum (or some other case)neck down to 338 and leave part of the 375 neck diameter un sized to head space the/a new 338 wildcat. I use the same process on other calibers when I don't have a belt to do the same thing when fire forming.

I suppose that any part of the neck that is not sized to the actual bullet diameter, or neck chamber,
could be called a doughnut because it is not the finished size for bullet tension.

But in my mind, the only place the term comes into play is when it is large enough to position the case for proper head space in the chamber.

Just My opinion

J E CUSTOM

 

[Edd]

In Yor pic I suspect the donut is on the inside of the neck. Run an expandrel mandrel in that neck and push it to the outside and take another pic

That's where donuts are. If they are on the outside, they are not called donuts.