Originally Posted by meichele
The simplest way I have found is to use a FL die and first throw away the expander ball. Then I simply run a case into the die. This forms the whole case including the neck. Then, I measure the outside diameter of the neck. Then I seat a bullet and re measure the neck. From there I can see how much I need to turn off the neck to get the desired neck tension. Then I turn my necks. Then I just FL resize them and call it a day. When they come out of the die, the body and necks are perfect and it is done in one easy step.
I have my current set up set to .003" of neck tension and only had to take a couple of thousandths off the neck.
Simple easy and it works.
Okay, good idea. It got me to thinking.
I just took a FL die out of the drawer for 300 win mag and removed the expander spindle. It sized the neck to .329" with very little runout. My 300 win mag is a factory without a tight neck so I do not normally turn 300 win mag brass. So if this brass is unturned then after firing all the variance in neck thickness is transferred to the inside surface of the neck.
So with a .329" outside neck diameter the math would be .329"-.308"=.021"/2=.0105". If I wanted a .003" bullet grip I would turn then necks to .0105"+(.003"/2)=.012".
The problem seems to me that you want the neck variations on the outside of the neck for neck turning. A very tight mandrel could push the variations to the outside where the blade would cut them but it can be hard to insert those tight mandrels.
So how do you get the neck thickness variations to the outside for neck turning or do you use a reamer?