I’ve just started turning case necks for a 300 Win Mag. Following the K&M instructions I sized the case without expander ball, used their 30 cal expander, then removed brass to just short of the neck shoulder junction. I removed less than 0.001” on most of the necks. When I seated the bullets, resistance was relatively light until the bearing surface got to the neck shoulder junction, where it noticeably increased.I also noticed the drill bog down when the pilot/cutter got close to that area. Is this the dreaded doughnut I’ve read about or is it because the brass is thicker at that point? I can’t see or feel with a paper clip any ridge in that area. What do you think? Thanks in advance for your replies.

Did the full diameter section of the expander mandrel go all the way through the neck?

Yes

There was likely some spring back from the thick part.

From your post I understand you were being cautious about turning down too far, but it's a balancing act. If you don't get down the neck far enough you can actually create a doughnut.

I think you used an outside neck cutter, correct. (That's what I use.) It's difficult to get the cut at the junction of the neck. Inside reamer would take care of that. They cost less than $10 I suspect.

I use a 21st Century neck turning tool. The cutters for those have the relief angle ground to match whatever cartridge I'm working with. That way I can cut all the way to the shoulder and even "skim a little color off" without digging in and creating a weak spot.

I skim the shoulder when I neck turn. If you leave any of the neck unturned you have the possibility of the "dreaded" donut.

Thanks for the replies. I've ordered an inside neck reamer, and I'll report back with results. Thanks again.

mathman, you were right on the money asking if the mandrel passed all the way through the neck and I thought it did, the taper on the mandrel threw me off. I checked the mandrel diameter and it's .308' and change, the bullet should have dropped right into the case after running the mandrel through the neck, but didn't, stopping at the neck/shoulder junction. I re-adjusted the mandrel depth, and lo and behold, the bullet now passes right thru into the case. The case necks need to be resized after turning. Now I'm waiting for a L.E. Wilson bushing die. I also adjusted for the cutter depth to just touch the shoulder. Thanks

NM, I don't know about your K&M, but with my Forster the inside reamer is meant to be used on fired cases, not sized cases. Using it on sized cases would result in necks which are too thin.

Yes, the one I ordered from LE Wilson is for fired cases, finished ID = .311-.3115”