BHuij
Active Member
So maybe I can clarify, because I think we’re on the same page.
My Lee full length resizing die does three things.
First, it sizes the body of the brass below the neck to SAAMI spec, including bumping the shoulder, assuming it’s screwed in to the default setting. I can control the amount of body/shoulder sizing happening by unscrewing the die a bit.
Second, it reduces the diameter of the neck by applying force from the outside. I believe my die is reducing the neck diameter to smaller than it needs to, and this is what I mean by lapping it out, so there is less unnecessary working of the brass.
Third, it re-opens the neck by drawing the expander ball back through it on the downstroke. My problem is that this operation is not expanding the neck enough, since my expander ball is aimed at in internal diameter of .311” after springback is accounted for (meaning the actual diameter of the ball is probably one or two thousandths larger than .311”).
The NOE expander plug fits into a different die and expands the neck on the downstroke, to two different diameters. I actually prefer to avoid this “stepped” neck diameter.
Seems like if I could replace the expander ball/decapping pin piece of my existing full length sizing die with a larger expander ball, I could get my desired neck inner diameter in the same step as my sizing, and avoid the stepped neck diameter. Ideally my “sizing” step would not mess with the full body of the case (which is already fire formed to the chamber), just bump the shoulder back and get the neck set to the right diameter.
Lee will make me a custom expander ball for $10. But I don’t know exactly what size I should get, because I don’t know how to predict brass springback. If I want a tension of .002” on a bullet which is .317”, what does the actual diameter of the expander ball need to be?
My Lee full length resizing die does three things.
First, it sizes the body of the brass below the neck to SAAMI spec, including bumping the shoulder, assuming it’s screwed in to the default setting. I can control the amount of body/shoulder sizing happening by unscrewing the die a bit.
Second, it reduces the diameter of the neck by applying force from the outside. I believe my die is reducing the neck diameter to smaller than it needs to, and this is what I mean by lapping it out, so there is less unnecessary working of the brass.
Third, it re-opens the neck by drawing the expander ball back through it on the downstroke. My problem is that this operation is not expanding the neck enough, since my expander ball is aimed at in internal diameter of .311” after springback is accounted for (meaning the actual diameter of the ball is probably one or two thousandths larger than .311”).
The NOE expander plug fits into a different die and expands the neck on the downstroke, to two different diameters. I actually prefer to avoid this “stepped” neck diameter.
Seems like if I could replace the expander ball/decapping pin piece of my existing full length sizing die with a larger expander ball, I could get my desired neck inner diameter in the same step as my sizing, and avoid the stepped neck diameter. Ideally my “sizing” step would not mess with the full body of the case (which is already fire formed to the chamber), just bump the shoulder back and get the neck set to the right diameter.
Lee will make me a custom expander ball for $10. But I don’t know exactly what size I should get, because I don’t know how to predict brass springback. If I want a tension of .002” on a bullet which is .317”, what does the actual diameter of the expander ball need to be?