.223 AI Donuts

[308 pilot]

My trainer rifle is a squared up Rem 700 in 223 AI. I have noticed that my brass (Lapua) is developing donuts or at least it certainly feels like it. Redding FL die with bushing. The bushing is not down to the shoulder, pretty far off to prevent that. I bought a Wilson reamer to cut the donuts put but that’s not really fixing it. I’d rather buy new brass and solve the root cause. Anybody help a guy out? Thanks.

 

[straightshooter1]

One of the reasons I like to use an expander mandrel instead of the expander button in the die is to better mitigate the donut issue. Doing so adds an additional step to my process, but it's worth it to me.

 

[pfl338]

Are the donuts on the inside of the case neck? That's were they typically occur, and a reamer will cut them out. If your talking about an area(ring) on the outside of the case just short of the shoulder then that is caused by the bushing die not seating far enough down the neck, which is ok and should not cause any issues in my experience.

 

[308 pilot]

One of the reasons I like to use an expander mandrel instead of the expander button in the die is to better mitigate the donut issue. Doing so adds an additional step to my process, but it's worth it to me.

I do not use the expander ball, I do use a mandrel.

 

[308 pilot]

Are the donuts on the inside of the case neck? That's were they typically occur, and a reamer will cut them out. If your talking about an area(ring) on the outside of the case just short of the shoulder then that is caused by the bushing die not seating far enough down the neck, which is ok and should not cause any issues in my experience.

Yes they’re on the inside. I have used a reamer to fix some of the brass but I’d like to solve the cause.

 

[Smithcollector]

The cause is just normal forward brass flow over time as the cases are fired. I also have donuts on 223 Rem brass, I used the Wilson reamer to cut out a surprising amount of material from inside the base of the neck. It can really be seen with a borescope. I also use a mandrel but it was not pushing the donut far enough out since I use an undersize mandrel to leave 2 thou tension on my neck. Turning the case neck, being sure to relieve brass a little into the shoulder juncture, will free up space for the brass flow and hopefully keep it from growing inside the neck, but I've tried to avoid that particular rabbit hole.

 

[XikoPlavi]

SAC dies and mandrel in one pull. I don’t have this issue with that setup (never have so far). You can also buy the sac bushing for your Redding die. Assume your using Redding bushing. I don’t wanna neck turn, but that’s just me

 

[straightshooter1]

I do not use the expander ball, I do use a mandrel.

If you're having to trim a lot to get the case length you want, you might have a headspace issue, as that can cause excessive flow into the neck from the shoulder resulting in donut issues like that. If one is bumping the shoulder back a lot when sizing, this too adds to the growth of the donut.

I don't load 223 brass, but with the brass I process I turn necks where I cut a very small amount off the shoulder next to the neck-shoulder junction. With that and the annealing I do allowing the mandrel does well to push the interior neck surface to the proper inside diameter, so I haven't had any donut issues. Though, most of the time, my loads are not seated quite far enough for the bearing surface to touch that area of the neck.

 

[918v]

I use a Lee Collet Neck Die prior to sizing. It squishes out donuts as they form. Lee makes custom collet dies. They can make you a 223AI die.