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Grinch

Grinch

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I am currently loading for a 30BR with 6BR Lapua brass opened up to 30 caliber. In such cases you encounter an inner bulge where the neck intersects the case shoulder, call it the "Dreaded Donut", if you will.

A 30BR will handle bullets up to around 125 grains and generally the best ones are flat base. In either bullet design, flat base or ocassionally a boat tail, the bearing surface does not seat down to the donut. It is common in other calibers that have been opened up, or wildcatted, to ream out the donut to keep pressures down. To my mind, this would particularly apply when the bullets would be ideally seated beyond the bulge.

For those of you that have encountered this situation, I would ask for your opinions. In my case, bullet seating to that depth is not necessary, nor probable, and I have no pressure indications. The loads are accurate. Do you see a need to ream out the donut?
 
I did my 6 BR brass 2 yrs ago. Expanded the necks, turned the donut out.

Now I only neck size half of the case neck rather than right to the shoulder.

I had no problems (mechanically) with them being there, no pressure, no seating issues, etc.

The problem I had was that I knew they were there and wanted them gone.

Ask Mick about his theory on donuts next month when you are here, he has an interesting take on them and that they may actually do good.
 
If it will still chamber, you're okay, I turn my .30 Br. necks and that gets rid of it. Mind you, my loads are very light compared to jacketed bullet users.
 
I had the same issue sizing 243 brass to 260AI. After fireforming I used a Forster inside neck reamer. Worked like a charm.
 
Are you guys talking about a fake double shoulder, like what we use on .303b to compensate for headspace? It looks like a little bulge, or donut, on the bottom of the neck where it meets the shoulder. I do this by partially sizing the neck, about 95-98% down. Now of course I don't recommend anyone else do this.

Is this a bulge on the top of the shoulder before the neck? Could you post a pic please?
 
Here is what I'm referring to.

260AI%20donut.jpg
 
Not talking about a false shoulder. Talking about a build-up of brass in the neck usually between the shoulder and where the bearing surface of the bullet is seated to.

On a fired case a bullet SHOULD drop into the case, if you have a donut(and its built up thick enough to matter) the bullet will stop at this point when dropped in.
 
Ceriksson,

CyaN1de has it right. My query is that if the bullet(s) don't touch the donut, is it a concern? You are spot on that a reamer (custom made) is the answer but is this necessary.
 
Grinch said:
Ceriksson,

CyaN1de has it right. My query is that if the bullet(s) don't touch the donut, is it a concern? You are spot on that a reamer (custom made) is the answer but is this necessary.
Click to expand...

It is only necessary if you are seating the bullets past it otherwise no.

You don't have to get a custom reamer. The Forster inside neck reamers work fine but you need the trimmer for it to fit inside.
 
Grinch

I have the Forster inside neck reamers in all calibers but only use them when the bullet is seated deep enough to contact the donut. These reamers should only be used in fired cases and BEFORE the case is resized otherwise you will remove too much brass and wreck the case.

Regards

The Whiteman
 
ceriksson said:
Yea turning the neck with an inside reamer is really the only way to remove the donut.
Click to expand...

Pushing the donut to the outside and using a K&M Mandrel on the neck turner with the carbide cutter on it works. Gets the outside and the residual inside from spring back.

Using an inside reamer would have to be done after firing and is much more finicky I would think.
 
CyaN1de said:
Using an inside reamer would have to be done after firing and is much more finicky I would think.
Click to expand...

Nope, run the case up into a trim die or neck sizing die, then ream it. The die holds the outside of the neck at a uniform diameter it's entire length. It's a better way because the pressure from firing has pushed the lump to the inside. You can never really push it back out the way 60,000 psi of pressure pushed it in. When you try, you end up with a little crease on the inside of the neck which turns in to little ring of thinner neck material after you turn the neck.

It can be measured if your neck thickness mic has pointed tips or with a probe like this:

P1050313.jpg
 
kombayotch said:
Nope, run the case up into a trim die or neck sizing die, then ream it.
Click to expand...
kombayotch said:
Kombayotch; You need a word of caution for those who do not have a bushing neck die. If you ream after neck sizing with a Forster neck reamer the case neck is now opened to just over bullet diameter. The bullet will now fall into the case without the required neck tension and the neck die you just used will not correct this. You now need a smaller bushing to give neck tension.

Your method will work very well with the correct bushings. As mentioned, I use the reamers only on fired cases because (a) It removes the donut and (b) I'm too lazy to take your extra step.

Regards

Aubrey
Click to expand...
 
Actually, I wouldn't use a bushing die at all as it doesn't get the entire bottom portion of the neck where the donut is. I don't ream after the sizing, I ream with the case still in the die. You have no control over the amount of spring back after you pull the case out. Putting it in the die brings the outside diameter of the neck to a consistent, uniform value. Then, I just choose the appropriate sized reamer to fit. One which fits the portion of the case neck that doesn't have the donut, without reaming out more than just carbon.

Reamers from reloading companies are limited to 0.001" increments, I use chucking reamers which you can get in 0.0005" increments, or smaller.

Even if you don't get the donut entirely, not sizing that area of the neck prevents whatever is left from interfering with the bullet. You've removed enough of it that the bullet clears it.
 
The instructions on the Forster Reamers say to use the reamer before resizing.

It only removes the extra material and touches nothing else inside the neck. works perfectly.
 
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