Initial Neck Turning / .284 / Doughnut Causing wobble

[Olde Man]

I noticed that when using the K&M carbide cutting mandrel that when seating a bullet deep the seating pressure would go high when the bullet pressure ring was in the shoulder neck junction. The reason is that the brass is thicker where it is surrounded by the shoulder. My solution is to size the case without a bushing and while the ram is still up use the K&M cutting mandrel in an old drill chuck to turn the new doughnut out by hand. When it is removed from the die the brass will spring back and will provide clearance moving this area away from the bullet.

 

[pat fulghum]

I noticed that when using the K&M carbide cutting mandrel that when seating a bullet deep the seating pressure would go high when the bullet pressure ring was in the shoulder neck junction. The reason is that the brass is thicker where it is surrounded by the shoulder. My solution is to size the case without a bushing and while the ram is still up use the K&M cutting mandrel in an old drill chuck to turn the new doughnut out by hand. When it is removed from the die the brass will spring back and will provide clearance moving this area away from the bullet.

@Olde Man ,
That is great for removing doughnuts after firing. What do you do on the INITIAL neck turning where that "shoulder neck junction" creates a pivot point for the neck?

 

[Olde Man]

I purchased my Dasher brass hydro formed and necked turned from Wes Johnson, P1zk. He always does a very nice job.

 

[Jay Christopherson]

I'll be honest, I'm planning to test a no-turn neck. I've seen it be really successful in a Dasher and I'm thinking that it could be super successful in a 284, setup right.

 

[Keith Glasscock]

@Olde Man
That is an interesting idea. Why couldn't we make a solid die that sizes the neck down, holds it in place, and reams it instead of neck turning? If we did that first, neck turning should be more successful because the pivot point would already be removed.

 

[Scott Harris]

I'll be honest, I'm planning to test a no-turn neck. I've seen it be really successful in a Dasher and I'm thinking that it could be super successful in a 284, setup right.

Jay, this fall I chambered a 284 WIN with a .320 neck and we used unturned Lapua brass. My youngest won the AZ State LR with it and came 3rd in the AZ State 600 Yd Championship, one point behind Jim Murphy. Based on this experiment, I'm thinking I have wasted a lot of time over the years turning brass!

 

[Scott Harris]

(Sorry for the long post)

My .284 neck turned cases (6.5x284 necked up) do not have a very consistent thickness when I compare them to my 6mm BRAI brass. With 6mm I can hold .00025 thickness variation pretty easy, but unless I do LOTS of work a single .284 cases will differ by as much as .001. Is this too much variation? I think so.

I use a 21st Century Neck Turning Lathe.

So I tried several things to get consistent thickness and I wanted to share my findings. What I found was that the doughnut at the neck shoulder junction isn't perfectly round and that the case would actually wobble like .0005 and that would cause the issue. Let me illustrate, the doughnut has bee highly exaggerated to make my point.

In this picture

View attachment 1034058

The neck of the brass is riding on the mandrel fine and I'm getting a great consistent cut, BUT.

Below, as the doughnut passes over the Mandrel the brass will open up some.. and the brass will start to wobble using the doughnut as a pivot point ever so slightly and change the thickness as it rotates.

View attachment 1034060



Exaggerated below...

View attachment 1034061


If I follow this routine.

1. Anneal
2. Neck Up to 270
3. Neck up to 284
4. Forster Full Length Size / Dwell
5. Expand / Dwell
6. Expand / Dwell
7. Expand / Dwell
8. Forster Full Length Size​
9. Expand / Dwell​
10. Expand / Dwell​
11. Expand / Dwell ​
12. Expand / Dwell​
13. Neck Turn​

I can minimize the doughnut and get much more consistent neck thickness, but man it takes a long time.

There has to be a better way.

Thoughts?

- Pat​

Pat,
​

I suggest the following.

1. Use a cutter where the cutter shoulder angle matches your case angle: PMA and 21st century both make these.
2. Do a rough cut on all your brass. Don't worry about how accurate this initial pass is, but cut into the shoulder a healthy amount to remove the donut. With the proper cutter, referenced above, it's very difficult to cut too deep. Our donut issues have completely disappeared since we switched to cutters with angles that match the shoulder (and take a nice chuck out of the shoulder).
3. With the rough cut complete, set your cutter up for the perfect final cut. It will maintain its settings well because the first pass opened up the neck and did most of the work.

That's it. With this technique, we can get about 500 pieces done in 2-3 hours. The initial rough cut is the key to getting good results on the second pass. Neck thickness is consistent to within a tenth.

Explanation:

I find it very difficult to maintain the cutter setting with both 21st Century and PMA tools when working on necked up Lapua 6.5x284 brass. The cutter constantly goes out of adjustment when hitting a tough/thick part of the brass. I changed my technique and achieve much better results now with less hassle. First, do a quick rough cut on all the brass. Then, re-adjust the cutter and do a second pass. This works beautifully and is way faster than trying to get a perfect cut in a single pass.

PS. I'd stay away from inside neck cutters. Turning on the outside and into the shoulder gets the job done better with less hassle. I'm also not a fan of roughing up the inside of the neck by using an inside cutter...."first, do no harm."

 

[pat fulghum]

... but cut into the shoulder a healthy amount to remove the donut.​

[/QUOTE]

@Scott Harris I appreciate the advice, but I don't think I'm communicating correctly...

The doughnut that I'm talking about is on the INSIDE of the case..... Yes cutting into the neck every so slightly gives it a place to go AFTER firing.
My concern is the initial doughnut (or the hard spot at the neck /shoulder which causes the pivot point)​

 

[Jay Christopherson]

@Scott Harris I appreciate the advice, but I don't think I'm communicating correctly...

The doughnut that I'm talking about is on the INSIDE of the case..... Yes cutting into the neck every so slightly gives it a place to go AFTER firing.
My concern is the initial doughnut (or the hard spot at the neck /shoulder which causes the pivot point)​

cut into the shoulder on your virgin brass == no donut (through 6 firings so far, not that I bother to check). I really think you are overthinking this a bit and getting hung up on a really minor (potential) issue in the grand scheme of things.

 

[Cowtownup]

Pat, this may sound like a crazy question, but how do you know the donut is there? Can you see it or do you feel it with say a paperclip bent open? The reason I ask, is like many others on this thread, I've turned quite a few necked up 6.5x284 cases for a straight 284 and I've not experienced the problem you are describing. I'm just curious if there is something else causing the problem and not the donut? I cant see how a donut could form from just running an expander mandrel down thru the mouth of the case.

 

[dskogman]

You could use Norma 284 brass and not have to worry about it.
It’s lasted as long as Lapua brass for me in 284.

 

[jhop28]

I have 4 years in shooting the 284 and shoot between 4 to 6 k rounds a year maybe I'm wrong here but its been my experience that the doughnut doesn't form until firing as I have to turn my new cases running a 312 nk and have never noticed it until they have been fired ?

 

[mikecr]

The doughnut that I'm talking about is on the INSIDE of the case..... Yes cutting into the neck every so slightly gives it a place to go AFTER firing.

My concern is the initial doughnut (or the hard spot at the neck /shoulder which causes the pivot point)

New brass, not yet necked up, has the least donut to deal with. That's a reason why it's best to turn at new condition.
As far as donut left by necking up, this can be mitigated by turning onto shoulder back when it was new.

Down the road, if you do a lot of FL sizing, brass thickness will move up cases into shoulders and into necks and eventually you'll be trimming away at it. A new donut forms with this, but it's not a problem unless you seat bullet bearing into it, or unless you FL size necks(including donut). This ugly situation is where inside reamers come into rational benefit.