I've heard and read mention of a donut which forms in the neck of cases. Can anyone offer a detailed explanation of what this is, how it occurs, if it affects the case for reloading and how to best remove it?

I know I'm asking alot but don't know where else to obtain the information.

Bobby B.

Sorry that I can't give you a complete explanation, but the donut is a ridge that forms on the neck immediately above the shuolder line. It is cause in the forming process. Precision Shooting magazine has had articles on the subject. Good luck.

I heard of many reports that the .243Win is prone to the 'donuts' mentioned above. They say it is brass flow and a case with thicker than normal walls are to blame. For this reason alone I did not buy a 243 Win rifle when I decided on a light caliber.

When you see one, you'll know. They got the name for a reason. I searched a while for a good pic, but wasn't successful, sorry.

As a case goes through the pressure of the explosion, the brass flows and sometimes forms a ring "donut" around the inside of the neck where it meets the shoulder. Inside neck reaming is easiest.

The do-nut is formed during firing and not sizing. Brass flows along the shoulder and doesn't make the turn to become part of the neck. It forms at the shoulder/neck



the most common way to detect the do-nuts is to insert a bullet down the neck of a fired and unsized case. If it stops at the shoulder/neck junction, then you have a do-nut.



I get them in my 280AI if I use Nosler 280AI brass. If I use 280 Rem brass then I don't get them, go figure!

It is a prerequisite that in order to have a detectable do-nut, you have to have a tight necked chamber. If you do not then you might have a do-nut but it is undetectable and has no effect. In a normal factory gun with a neck clearance of .005" to .012", the neck will expand so much that the do-nut will be recessed enough so the bullet base won't catch it.

Reaming is the best way to get rid of do-nuts and that is what I do with my Forster hand held turner with a reamer attachment.

Just slide a bullet down the neck, chances are you don't have the do-nut problem. However if you do then they can make a difference

Let's not confuse this with a doughnut that will form on the outside of the case at the junction of the neck and the shoulder when you neck size with a F/L die and do not size all the way to the shoulder. Then, after a couple of firings, a small doughnut will form that is merely the neck not sizing down. It does no harm and IMO helps align the case in the chamber.

Agreed...

quote:

Originally posted by wasbeeman:
Let's not confuse this with a doughnut that will form on the outside of the case at the junction of the neck and the shoulder when you neck size with a F/L die and do not size all the way to the shoulder. Then, after a couple of firings, a small doughnut will form that is merely the neck not sizing down. It does no harm and IMO helps align the case in the chamber.

Thanks guys. Here's my next question, "Will I get a donut in my 6/284 brass?" It is necked down 6.5/284 Lapua brass. The neck die was a Redding 'Type S Match'.

Bobby B.

Is the doughnut common on police ammo?

quote:

Originally posted by Bobby B.:
Thanks guys. Here's my next question, "Will I get a donut in my 6/284 brass?" It is necked down 6.5/284 Lapua brass. The neck die was a Redding 'Type S Match'.

Bobby B.

Do you know what the neck dimensions in your chamber are? For 6mm it should be around .270" to .276".

If you don't have a tight necked chamber and do have a lot of neck clearance then you will not get do-nuts. Even if you have a tight necked chamber it is not a certain thing.

The only way to tell is to check the fired cases.

Again the sizing process or the sizing dies are not responsible for do-nuts, at least the internal ones.

I'll have to check what the neck dimension is, but I do not that it is not a 'tight neck' chamber.

Thanks for all the help. I've been reloading for 30 years but never really was aware of 'donuts' until recently.

I used to neck down 7x57 brass to establish a secondary shoulder to use in fireforming 7x57 brass into a hot 6mm wildcat I dreamt up and never experienced any adverse results as far as accuracy was concerned, even after repeated loadings. The bullet wasn't seated very deeply into the case though.

Bobby B.