K+m turning mandrel
- Thread starter AJC
- Start date
Do they advertise that it will get rid of the doughnut? There are turning and expanding mandrels, the turning mandrel goes in the turning tool and the expanding mandrel expands the cases for a perfect fit on the turning mandrel. People have re-purposed them for getting nice neck tension instead of using a bushing (turning = 2 thou, expanding = 1 thou) as well as for creating false shoulders in wildcat fireforming.
I am no expert by any means so take what I say with a grain of salt. The brass will always spring back a little, so I would bet that it may make the doughnut smaller but not completely eliminate it. I know there are inside neck reamers that can get rid of the doughnut and I have read that people will cut into the shoulder a little when neck turning to try to reduce the chance of the doughnut forming (21st century has cutters that have the angled part so the shoulder can be cut into safely). I also know a lot of people just try to load the bullet so that the boat tail is above the neck shoulder junction so that it is less or not impactful.
Kyle Schultz
Gold $$ Contributor
Yes and no. Even K&M shrugs their shoulders when asked.
Their guidance is to NOT run the expander through the entire neck. Stop just above the suspected donut. Then they recommend inserting the case onto the pilot prior to starting to rotate the case. You may or may not cut any of the donut. By the simple fact you have to have clearance between the inside of the case neck and the pilot (in order for the case to rotate), I don't see how you could ever hope to cut it out entirely. But I will guarantee that you will score the inside of your necks trying.
My departed internet friend and case prep mentor, Jim Hardy, hated the damn things. My original 7mm pilot was fluted. I had the tips ground down but still had occasional scoring. Since then, every K&M pilot I have ordered has been smooth.
The best solution is set the free bore on your reamer so that the pressure ring or bearing surface of the bullet is seated above where the donut lives. If you do that, it will never give you a problem. My dos centavos.
Their guidance is to NOT run the expander through the entire neck. Stop just above the suspected donut. Then they recommend inserting the case onto the pilot prior to starting to rotate the case. You may or may not cut any of the donut. By the simple fact you have to have clearance between the inside of the case neck and the pilot (in order for the case to rotate), I don't see how you could ever hope to cut it out entirely. But I will guarantee that you will score the inside of your necks trying.
My departed internet friend and case prep mentor, Jim Hardy, hated the damn things. My original 7mm pilot was fluted. I had the tips ground down but still had occasional scoring. Since then, every K&M pilot I have ordered has been smooth.
The best solution is set the free bore on your reamer so that the pressure ring or bearing surface of the bullet is seated above where the donut lives. If you do that, it will never give you a problem. My dos centavos.
They have two mandrels that I have seen. One has no teeth and the other is toothed.
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