K&M neck expanding iron help

[Egg]

I am using the K&M neck expanding iron to smooth out some new 6.5 284 Lapua brass. The expander manderal runs pretty smooth untill I get down to the neck/shoulder junction and there seems to be a "donut" at that point because I can slip a bullet into the neck and it stops there.

Question- am I supposed to run the manderal past the neck/shoulder junction? Do I stop at that point and use a .2655" reamer to remove the donut or do I leave the donut there if my 140 gr bergers not get seated that far down?

Thank you in advance
Egg

 

[Patch700]

Yes.. You run the brass up onto the mandrel untill it has completely passed through the neck.. If this is new brass you are not seeing a donut as per say , but merely a portion of the neck not yet expanded enough to accept a bullet.. Run it in further.

 

[Patch700]

Some pics for a reference .

 

[Patch700]

Neck fully up on mandrel without riser die.

 

[Patch700]

Neck fully up on mandrel using riser die.

 

[Egg]

Patch700...thanks for your time and setting this rookie straight!!!!
Egg

 

[Patch700]

You're welcome.. Remember that there are different types of mandrels for different types of jobs. In this instance I assume you are using an oversize mandrel to expand the necks and then merely resize them so you are acheiving a more uniform neck grip.

In any case , even if you are using a mandrel to expand necks so that they will have a proper fit to the matched mandrel used in a neck turning tool the same principle applies.

There are also mandrels used as a finishing tool for final neck ID. and the same principle would apply here , you run the brass to it's full neck length to ensure a constant diameter from top to bottom.

Good luck and enjoy the upcoming holidays.