Home Forums Hunting & Shooting Ask The Gunwriters how to outside neck turn

Enlighten me:

What is the big deal about a "dreaded donut" inside a neck.

Just exactly what are the problems? What does it do ?

I'll have to say again that my Quick Load throws out some phenomenally sensitive variables amounting to thousands of PSI and Velocity.

But I just don't have a handle on this "donut"

If you have good coffee, donuts are not a problem.

Short version: It messes with proper bullet seating and can cause chambering issues as well.


Side note: I believe you have a QL addiction.

Gotcha. Agree.

Those bullets that are long and protrude down in the case to meet COAL may meet some internal obstruction. However, they will push out the donut and cause some infinitesimal friction grip.

Is it actually measureable and it is it even significant?

It is significant, it is measurable, it can and does mess things up. Inconsistent bullet grip, runout issues, et cetera.

Big Time. And worse.

Here's an example and my first experience with the donut.

I formed 7 Mashburn Super brass from .300 Winchester Magnum brass. I had previously neck turned the new .300 Winchester brass before forming the 7 Mashburn. After running it through the die, it was obvious that the shoulder was pushed back and the neck of the Mashburn was longer, now comprised of part of the shoulder of the original .300 WM brass. I had turned the .300 WM brass down and into the shoulder a bit as I always do to actually avoid forming a donut.





The donut was obvious, but I thought it wouldn't matter since it was going to be on the OD anyway after sizing with the expander ball or expander mandrel before doing any bullet seating. I proceeded with load development and really had a difficult time; I couldn't find an obvious node in the ladder. I tried a couple of loads in the ladder and shot them for long range groups as well as 100 yard groups.

Long range groups were horrible with tons of vertical. All over the place. The 5 shot 100 yard group was pretty good.



Thinking it may be a seating depth issue, I went out and shot a test. It didn't improve anything. 550 yards with well over an MOA of vertical stringing...





Then I got to thinking about the obvious donut at the base of the neck on the brass. Threw some calipers on it and measured it. Checked the reamer diagram for neck dimensions. Chamber neck dimension was .317" and the donut at the base measured .317" to .321". Compound that by seating a bullet in the sized case and pushing it out another .002" and you have a big problem chambering a round. The bullet was being squeezed big time when the case was chambered in that little donut area.



The real telltail was taking a fired case and slipping a bullet into the neck. It should slip in freely all the way. When this was tried, the bullet would stop in the neck when the bearing surface in front of the boat tail came in contact with the donut that was now in the ID after being fired.

I ran the existing sized brass through the expander mandrel, neck turned off the donut all the way into the shoulder a tad, loaded 10 and went to the range with the load I had.

Vertical was cut in half and accuracy was much better.

I'll have to reshoot load development because I'm sure the results were inconclusive due to the ff'd up brass.

This is one of the best ever posts. Fantastic. I love it.

I read it twice, but wait, I'm the inveterate pain in the ass. B

I'll pick it apart maybe needlessly.

When I fire form with pistol powder and a wax plug instead of a bullets, it extends the neck. I'm speaking 6PPC. I have to expand the neck about .006 and then turn kissing the shoulder neck juncture. I have no donut doing it this way and the neck expander does very little and does not push the neck back.

Running the expander mandrel into the fire formed, sized brass, then neck turning to eliminate the donut yielded great results.

Same load as before. The last 3 went into less than one inch at 600. Vertical stringing was eliminated completely.

Must have had a breath of wind at about 1/2 MOA

Nice! That sure came together for you, Rick!

RC
That post is worthy of inclusion in a reloading manual. Good info. Thanks

The best I've ever used:

TN1 by Rick Mulhern, on Flickr





TN2 by Rick Mulhern, on Flickr

If you click on the photo you can see that the shoulder is just 'lightly skimmed'! Cartridge shown is Lapua 30/06 brass and I run the case up into a mandrel measuring .3075" prior to inserting the arbor of the turning tool!

The results?

Five shots from 800 yards. The rifle/ammo will do this quite often for me.

Beanland06 by Rick Mulhern, on Flickr