Doughnut Problems?

[Changeling]

I keep hearing about this problem whan guys go to a new chamber, usually an Ackley. I absolutely do not understand it!

When you say "Dougnut" are you talking about the neck to case shoulder junction at the "inside" of the case ? Please explain what causes it.
Changeling

 

[jb1000br]

Yes

With several firings it can form from the shoulder brass flowing into the neck area, or it can result from improper neckturning.

Just a fact of life, and not a real problem if the bullet is seated ahead of it.

YMMV,
JB

 

[ReedG]

I've got a couple of reamers coming,.241" and .242") to use in my Norma 6 BR cases. After about 6-8 firings I start to see the doughnut and it gets progressively worse with more firings. I wonder if it doesn't, at some point, start to introduce a venturi-effect or other interference to the burning powder gases?

ReedG

 

[Changeling]

Guys I have "never" experienced this phenomenon in any of my chambers. I have had several rifles chambered in 6mm Ackley and 280 Ackley, both with 40 degree shoulders. I even cut two cases lengthwise with a hacksaw last night, no sign of a "donut".
If I did have this problem I would just "inside" ream the neck to just clean it out because it definitely would change the turbulence configuration of ignition. To what degree this type of condition would affect accuracy I do not know.
However, how come I have never experienced this in my chambers?

 

[Forum Boss]

One of the benefits of the 40-degree Ackley shoulder is that it retards brass flow into the neck-shoulder junction. A tight-fitted chamber also helps. I had a Rem .260,std 20-degree chamber) that formed doughnuts so fast I could not seat a medium weight bullet and still chamber the cartridge--this after only two firings. I have a friend with a .260 Ackley in a tight chamber. He has no doughnut problems. We both started with Lapua .243 brass, necked up to 6.5mm.

As others have noted, if your chamber is throated to keep the bottom of the bearing surface at least .050-.060" from the doughnut area, you usually can avoid the problem.

In order to fix my .260 problem, I had to full-length size to sharpen the NS junction, then inside ream with the K&M cutter-tipped mandrel. Then, to prevent recurrence I outside neck-turned the last 1/3 of the neck and up into the shoulder about .030" per K&M's recommendation. That worked, but what a lot of effort!

 

[Changeling]

Moderator, I can "Feel Your Pain" if you had to go through all that. The only thing I can tell you about my reamers is that they were minimum specifications, 40 degree shoulders with no turn neck,kiff made them).
I had the gunsmith chamber for a definite "Crush" fit. This meaning that when I closed the bolt on a new round to be "Fire Formed" that the bullet and the case were "Forced" into the chamber on the down shift of the bolt handle, a definite crush fit that you can feel. This produced perfect cases with very rare case loss.
I reload on the warm side, but have found to my satisfaction that this method has produced great cases with out any indications of "head separation". Why I don't get the "donut" I don't know, but there has to be something in the way I do it, or I would have experienced the phenomenon.
Changeling

 

[Changeling]

This is really starting to bug me! I searched through some old notes and found some more information, whether it has some bearing on the situation are not, I really don't know !
If anyone having this problem tries this, please post, I really want to know.
The only thing I could find any different from what I said was:
1. Comment. I am using long bullets to form the cases. They are a considerable length into the powder supply.
This rung a bell and I remembered using a load of hotter powder because I had removed some of the combustion chamber by seating the bullets "Past" the neck shoulder junction! I had got a hell of a deal on 1000 bullets and used them,Shotgun News).
Whether this has some bearing, I don't know!