How to Identify a Neck Donut?

[Tree Farmer]

I'm no expert, but I recently had the donut issue in two different cartridges (first time for me). I was having difficulty closing the bolt on a loaded cartridge and thought I needed to bump the shoulder more. After firing the round, I could not slide a bullet completely down the neck (the donut stopped the bullet because the extra brass was pushed into the neck after firing). I removed the donut by neck reaming, but also could have resized (pushing the donut to outside of the neck) and turned the neck to remove excess brass.

 

[ronstone09]

On the fourth firing (third time reloaded) the bolt lift is stiff, velocity is about the same. On the first through third firing the bolt lift is smooth and velocities steady. The shoulder is set back .002-.003" and I have begun annealing after each firing. I trim after fire forming and need to again after the third or fourth firing so case length doesn't seem to be the issue.

Be careful with your shoulder 002 is sufficient ! More than that and you can get into head space problems and case separation !

 

[L.Sherm]

Be careful with your shoulder 002 is sufficient ! More than that and you can get into head space problems and case separation !

Its gonna take alot more past .002 to get into case head separation. I know of some BR guys go .005- .006 and even heard of one bumps .008

 

[Rflshootr]

How do you identify the dreaded neck donut? Can it be seen inside the neck with a bore scope? How many reloading's does it take to form if using a bushing die? Would it not be forced to the exterior if expanding with a mandrel? I just started using a Redding bushing die so I've never had to deal with this before.

Here is one of my Lapua cases that have been fired 24 times in 222 Rem without ever annealing. The bullet isn't seated down to the donut but I started noticing the rounds chambering hard. I pulled the expander ball, sized a few and I measured the neck, then pulled an expander ball through and re-measured to find a .0035-.004 gain for about .06 above the neck/shoulder junction. Just so happens that it fit my neck turning mandrel almost perfectly. So I skimmed the neck off. And they still shoot pretty well for an old model 722 sporter built in 1952.

 

[Just ken]

Have a 22-250 AI with donut problems. Reloading with a Redding turret press, can feel the donut when seating the bullet, goes in with normal force until bullet hits donut, then requires addition force indicating the donut.

 

[Mikecr]

Ken, all you need to do is size above the donut. Let it expand on firing -away from seating bullet bearing.
There is never any 'good' in sizing to bring donut into tension. With this, most should not be FL sizing their necks.

 

[Rflshootr]

Ken, all you need to do is size above the donut. Let it expand on firing -away from seating bullet bearing.
There is never any 'good' in sizing to bring donut into tension. With this, most should not be FL sizing their necks.

Until it gets bad enough that you have to do something about it.

 

[Mikecr]

True, but you might accept that it took your choices, and actions, to get there.
Consider this while solving the issue.

When it's implied that brass 'flows', like donuts will build no matter what?
In every case there has ever been of donut addition, it was the reloader who caused it.
For those of us understanding this, and choosing not to cause donut issues, we don't have them.
We don't have to deal with it -ever.

I iterate this, not to be a jerk, but because problems are best solved nearest the root causes.
For example:
- You notice loaded ammo runout is increasing with each reload cycle
- You worry about it
- You ask around and get a handful of silly tricks (didn't really work)
- You swap dies & migrate to a different sizing plan (didn't really work)
- You dig in and learn about the root cause of runout, then culling new cases with offending thickness variance (works)
- While in the learning mode, you figure out that for YOUR situation, bad runout won't affect YOUR results anyway
- You stop worrying, and now well on the way to stop worrying about a lot of things -that YOU control
Will you be listening to a mob then? Not so much

 

[Roninco]

Ken, all you need to do is size above the donut. Let it expand on firing -away from seating bullet bearing.
There is never any 'good' in sizing to bring donut into tension. With this, most should not be FL sizing their necks.

Since my bushing die does not resize to the neck-shoulder juncture I can measure a diameter difference between the top and bottom of the neck after sizing/expanding to identify the donut?

 

[Rflshootr]

Mike what you say is absolutely true, but not everyone is using a FL bushing die.

 

[Rflshootr]

Since my bushing die does not resize to the neck-shoulder juncture I can measure a diameter difference between the top and bottom of the neck after sizing/expanding to identify the donut?

If you pull an expander button thru, yes.