Help fix my donuts

[sp6x6]

I read and posted on last thread on this. I have them, i think seating my berger hybrid out towards lands my have developed this some. When seated it looks like the boattail is slight above shoulder neck. The brand new brass is 5-6 thousands short of fired on shoulder, chamber leaves a small brass line 1/32 above neck / shoulder. I have a K&M neck with carbide pilot w/flute, I ran this in on fired case, do I DO THIS ON SIZED. On the fired the bullet will just rest where it was seated. I reamed a fired but I STILL could not slide bullet in, notice my reamer supplied pilot fits a sized case also. Dont have a mic, but pilot supplied with K&M,was about .335-.336

 

[Rocky Mountain]

Size the entire neck then run your K&M expander mandrel down the neck then run your K&M carbide fluted turner mounted pilot all the way through the neck cutting the donut away. You have to do it this way to get best neck fit with the carbide fluted pilot.
Hope this helps

 

[Mikecr]

You might have a doughnut, but nothing described causes or indicates one.
I'll gamble to predict fairly close neck clearances here combined with fairly high downsizing of necks (oversizing).
Bullet seating is re-upsizing a portion of your necks (which is normal).
After firing you find that a bullet will slide into the bullet seating/sized portion of the neck and stop where bullet seating did not size the neck.
That in itself, thought to be a doughnut, could merely be local springback variance as a result of sizing actions, that are not really a problem at all.

This would explain why it all began when seating depth was reduced (which does not cause doughnuts).

 

[sp6x6]

Rocky Mtn, I just did whatyou suggested Mikercr, I am trying to sort this out , a bench buddy of mine that is out of town looked and said I had donuts, it looks to me like you can see a weird band down in neck. He said it was odd for me to have a donut, he loads 6mm dasher.I started with new norma brass, 4.069 on .420 bushing, fired 4.075, I had to size it seemed to 4.073 or 4.072, not at first with brass short. But this was to close bolt easy, in beggining I pulled spring so I could really feel bolt.Then I shot hyb.touch was 3.845 or coal of 3.682, I WENT 3.840 on comparator. This appears to put boat tail above the shoulder / neck junction. When I fired the new brass youcould see a clean line of brass about 1/16 above the shoulder, this got a little lower as sized more. I full lengthed all but new, then just neck area. On 2-3 to 4 I full lengthed to the 4.072, .001 less before that.When I was loading I decided to try some 285, which I WAS GOING to seat deeper. I had checked all brass for fit, when I tried the 285 it was tight, but the hyb, was smooth. I was not in lands. I put a .375 bushing on my comparator and my rounds where growing more with the bullet seated deeper, buy a bit. I took sizing way past and down to 4.065, I knew I did not want to size that far, so gave up and loaded the berger. But the neck shoulder junction was causing me problems and the gun seems picky in that area. I started with a tapered lapua bushing gauge and the farther I read toward shoulder seems to mean less for fit. Since this is so long, my next ? is what do you think on how much neck sizing IM getting and what route to lessen, it is 338 nm,didnot see a bushing bump die.Neck shot.370,loaded.365, out of sizer .364, your thoughts appreciated