Donuts...

[lurcher]

Just trying to get my head fully around the whole inside neck donut thing. Do I have this right?

It can occur when either necking up or necking down? is it more likely to happen one way or the other?

One cure is to neck turn and be sure to kiss into the shoulder. This should be done before or after necking down? Also it is wise to FL size with a non bushing die that gives a sharp shoulder prior to turning with new brass?

detecting them can be done using either pin gauges or a with a bullet in a fired case.

Once you have them the only way to rid yourself of them is to inside neck ream with something like a K&M neck turning reamer mandrel.

Will they have any effect on accuracy if you are not seating deep enough to reach the donut?

Can you get donuts anywhere except the shoulder neck junction. For instance if you partial neck size with a Lee collet neck die or bushing die can you get them further up the neck.

Do sloppy factory chambers contribute to donut formation. Is it possible to get them with a factory chamber and unmodified brass (not neck turned).

Will they form on normal calibre (not necked up or down) brass that has been neckturned and the operator did not kiss the shoulder.


I have noticed that with my norma 7-08 brass (not neck turned) fired in a factory-chambered rifle that when UI seat with a wilson seater the bullet slides in and then further down I feel like I am passing a restriction just as the bullet reaches close to full seating depth, could this be a donut effect?

Thanks in advance for your thoughts
Lurcher

 

[dennisinaz]

You asked a lot of questions, but here is my take on it in a nutshell. When you neck UP, you are creating a neck out of brass that is from the shoulder. Sometimes this brass is thicker than the neck brass. Depending on how far up you are going will, to some extent, determine how bad your donut it. I get them when I neck .243 up to 260 Rem. I do not get them when I neck 308 DOWN to 260 Rem.

When I neck down, I like to neck turn FIRST. This pushes a small amount of NECK brass into the shoulder. This is better than the opposite situation. Sometimes I will still make one final pass on the finished brass but this is only to remove a few 10th if I have done it right the first time.

As far as getting rid of them, I use a .250 chucking reamer on 260 brass. I spin it in my lathe and hold the reamer in my hand. I then put pressure on the case with my thumb and move the reamer in. I hold it on a slight angle as to not affect the rest of the neck. It strip the donut off right away.

I don't think the donut hurts a thing if you are shooting light varmint bullets that aren't seated deep enough to touch it.

 

[artbosco]

Will they have any effect on accuracy if you are not seating deep enough to reach the donut?

Most short range "B"enchrest shooters pay little or no attention to the donut, if formed.

 

[JohnnyJohnson]

Will they have any effect on accuracy if you are not seating deep enough to reach the donut?

Most short range "B"enchrest shooters pay little or no attention to the donut.

Except for the glazed or powdered sugar donuts.