204Ruger

So I finished building a 6x45 and am having a tough time finding a really accurate load. I bought some new lapua 223 brass and using a redding die, expanded the neck of the case to 6mm. After firing the rounds 1 time I have a pretty big doughnut inside at the base of the neck that is located where the shoulder was expanded into the 6mm neck. It will not let a bullet pass through on a 1x fired case. I can't imaging this doughnut not affecting accuracy. Thought about getting a reamer to remove it, but if I run the brass through a full length sizer, the doughnut is mostly gone. After full length sizing, the ID of my neck measures at .2425, but the ID at the location of the doughnut is .242. Do I need to worry about that .0005"? Any thoughts or opinions?

Yep, the donut is a fact of life when reforming/necking up/down.

K & M makes a tool specifically for removing this pesky issue, and it seems to be very well thought of among the accuracy crowd.

https://www.kmshooting.com/

As long as the bullet is not coming in contact with the portion of the neck that's harboring that .0005" bump, no worries. The amount of influence that will have on the burning characteristics of the powder will be minute.

HTH

Thanks for the quick reply, I was hoping for an everything is good to go, but I had a feeling I was going to need to get me a reamer. Hopefully, that will shrink my groups down.

When you size it, you move most of the doughnut to the outside. When you fire it, the chamber moves most of it to the inside. Best, just to get rid of the excess material. Inside reamer or outside clean-up, you can get good results either way.

RAMOS wrote:Inside reamer or outside clean-up, you can get good results either way.

Jon's right, and IMO, the best/easiest method is just to do a clean-up outside neck turn after sizing with the expander button in the neck die. Wha-la, no donut.

Cheapest and easiest way to get rid of them is to get a Forester "inside neck reamer'. You will need a Forester case trimer. You put it on trimer and run it into a fired and unseized case. This should be a one time thing. Midway sells them for $24.50