Home Forums Hunting & Shooting Ask The Gunwriters "dreaded doughnut" - MD

John, I read a while back that you use a neck turner to eliminate the "doughnut"
It seems to me a reamer would be necessary.
Can you school me on the process you use?

I just size the case with a standard expander-ball die. The expander-ball "pushes" the doughnut to the outside of the neck, where it can be lathed off.

What exactly is this "dreaded doughnut"?

It's a thickening of the base of the neck in bottle-necked cartridges, which can result in poor accuracy, or even excessively high pressure, because of the "doughnut" being pressed around the bullet when the cartridge is chambered.

It normally occurs for two reasons:

The process of firing and resizing the cartridge. This tends to move brass forward in the case, and the top of the shoulder (which is thicker than the neck) starts to "migrate" into the bottom of the neck.

Necking cartridges up in caliber, say making .260 Remington cases from .243 Winchesters. Again, the top of the shoulder becomes the base of the neck.

But I have also occasionally encountered new factory brass that had slight doughnuts.

It has been a while but I got some WW in 7mm08 that had bad doughnuts.

Mule Deer, thanks for the explanation.

Why couldn't an inside neck reamer be used to remove it? Does that cause a problem?

K&M makes a handy turning device that cuts in and out simultaneously

An inside reamer can easily remove the doughnut. But that doesn't mean it will leave the neck the same thickness all the way around, partly because with a lot of "standard" mass-produced brass the necks tend not to have the same thickness. This can definitely cause accuracy problems.

Outside-turning not only remove the doughnut but insures even neck thickness.

Ah so. Thanks.

“Doughnuts” have little to no effect on accuracy if you have a chamber that allows the pressure ring on the bullet to be seat above the neck should junction. ( where the “doughnuts” live )If you do have chamber that will allow this, it’s hit or miss that the loaded round will still fit in the magazine. ( assuming you handload )

It’s only a couple or so of the latest cartridge designs that take “doughnuts” into consideration. 300prc comes to mind.

Wouldn't the "donut" issue be mostly confined to match chambers with tight necks?

No. It's a pain in the ass with factory chambers too. It screws up bullet seating.

That sucks, I have necked up 40 or so cases of 243 to 260 and have yet to see anything resembling a problem.

It doesn't always occur.

My experience indicates more problems with cases necked up, rather than down. For instance, necking 22-250 cases up to 250-300 AI. A "doughnut' will develope at the neck shoulder junction. I found this on my 2nd firing of the cases..sized cases chambered fine, but when I seated a bullet, the doughnut was pushed out, making for hard chambering. My normal sequence when loading is to try both empty sized brass in the guns chamber, then the first charged and seated case. So I only had one loaded. I ended up outside neck reaming. Getting a little smarter, I found I could discover the doughnut by fitting a bullet into the fired case. The bullet would stop at it in the neck. Those fired cases I inside neck reamed.
I now use plentiful 6.5 Creed cases, neck down..no problems.

It's one of the reasons for David Tubb's 6XC as well--which is the .22-250 necked up and with the shoulder also pushed back. It will fit in standard shot-action magazine about 2.85 inches long, and even 115-grain high-BC bullets won't seat down into the shoulder/neck junction.

As mathman noted, it doesn't always occur, but can after a number of firing/sizing cycles. Which is why I eventually started necking .270 cases down for my 6.5-06, rather than necking .25-06 cases up.

Thanks, John.

Well I am going to watch that brass. I have annealed the first 20 pieces I got hold of, actual antique Remington 140 gr. Factory ammo. Each piece has been fired at least ten times.Retired. But the 40 or so pieces of Winchester 243 brass necked up is expected to last ten firings also so I will watch for the creeping doughnut. I hated doing it but I necked down a box of 7-08 Winchester brass to 260 and also some PPU 308 brass and another 20 rounds of Federal 308 brass. All have been loaded and fired at least once. Though presently I have slowed my primer popping down a lot.

Will bushing dies eliminate doughnuts? Particularly because of how much of the neck they do or do not size?

Thanks Mule Deer, for the heads up on necked up brass.
I recently made some 338-06 brass by necking up some FC and Win 30-06 brass I had first annealed. It "looked" great, but this thread inspired me to check for doughnuts. Some of the Winchester brass (the first batch I've checked, in the process of neck turning) is particularly bad, so much so that the neck turning mandrel almost sticks in the case (which has already been passed over the sizing mandrel) when the turning mandrel reaches the constriction at the base of the neck. The brass is NOTICABLY thicker there.
I'm pretty fat on .35 Whelen brass so I am considering just abandoning necked up 30-06 (which I have a ton of, thus my desire to use it) and just go to necked down .35 Whelen.
I have some Weatherby headstamped 338-06 brass but I prefer to use that exclusively for one of my two 338-06s, and differently marked brass for the other, since their chambers and throats are slightly different.

Anyway, thanks again - this may explain why the "other" 338-06 has not yet shot as good as the one getting the Weatherby brass.

Rex

John, about an hour after I got back on this thread, I found your explanation in Rifle Loony News II, which has been my evening reading for a little while.

One well-known benchrest competitor claims bushing dies tend to encourage doughnuts, though in the article I read he didn't explain why.

That has not been my experience. In fact the dies for my own 6mm PPC benchrest rifle are Redding Competition, and I haven't detected any hint of a doughnut in the brass since starting to use it years ago. But then I don't shoot in matches. Instead I acquired the rifle to test what factors affect accuracy.

Some bushing dies stop shout of fully sizing the neck shoulder juncture, others have an angle that matches the shoulder and don't leave a ring un-sized. The Wilson bushings have the taper, I am not sure which others do.

When neck turning to remove a doughnut how much should you take off? Will just a 50-60% skim turning be enough or will that aggravate the problem?

An "un-sized" portion of the rear of the neck is not necessarily a doughnut.

If you use the technique I suggested in an earlier post, resizing the case in an expander-ball die, the doughnut will show up on the outside of the base of the neck, and be measurably larger than the rest of the neck. Setting the neck-turner to just skim most of the neck will eliminate the doughnut if you just turn the very top-end of the shoulder.

How many thousandths of an inch does this donut comprise of?

My size gets larger in the middle with donuts. That's why I don't consider them food. Be Well, RZ.

Depends on how large the doughnut is. It will vary.

When I was sizing 6mmBR brass up to 30BR , what had been a portion of the shoulder became the bottom of the neck.
Had I been loading bullets that seated their base below the neck/shoulder junction, I would have had a problem with the doughnut.
I turned all the necks for uniformity as I had a tight neck chamber and the excess was trimmed off neatly, including the doughnut.

[quote=Mule Deer]An "un-sized" portion of the rear of the neck is not necessarily a doughnut.
[/quote

If you use a conventional FL sizing die afterwards without the expander it can force the midriff bulge to the interior and form a doughnut. Some like the bulge as they think it helps to center the case in the chamber, not sure about this one though. I only turn necks if forced to and then my cutters have the bevel on them.

This is sound advice, however if you are one of those that is really fastidious, you may feel the need to anneal the brass before this process.Theoretically less spring back going over the mandrel and more doughnut to the outside. I say theoretically because I have not actually measured the difference...... but fairly certain the difference would be measurable.

BUT - does it matter?

Edited to add:
The difference in annealed and not annealed, that is, Will the brass "spring back" that much?

Was going to post pictures of 'lumps' vs, 'donuts' but posting pics here leaves a lot to be desired -Al

Imgur......

Forget the 338-06 just roll with the 35 Whelen

Imgur is what I use. It doesn't want to play nice here for some reason. Finally slapped it around and got it listen to reason.

'The lump' on the left: -Al

Al, just what are you manufacturing, there?

It guess would depend on how hard the brass is.

I just know if I’m going to go through the trouble of cutting off a doughnut, the brass is probably due for annealing.

Brass is the most labour intensive part of the whole reloading operation. Without good uniform brass , you can’t achieve bughole groups.

Sorry to quote my own post, but I got around to neck turning the 338-06 brass I made from Federal 30-06 cases and it is MUCH different than those I made from Winchester 30-06 cases. I can only surmise that the brass in the shoulder of the Winchester cases is a lot thicker than the brass in the shoulder of the Federal cases. Which is funny since the federal cases weigh more. I had annealed the neck and shoulder area of both batches pretty well the same, so I don't think hardness was the factor. The Federal just neck turned a lot more smoothly than the Winchester. It seems the doughnut on the Winchester brass was far more severe.
Just an observation.
Rex