My experience is that if your expander ball has to increase the neck OD by more than 0.002", it will pull the case neck and increase the TIR. That is even with using a carbide expander, lubing the inside of the case neck, and setting the expander high (so it exits the case mouth just as the neck comes out of the neck sizing portion of the die.Would someone please explain the advantages of using these over an expander ball?
thanks, I have the Sinclair Gen II and I was wondering a while back if the 21st Century mandrels would fitI have had very good luck using the 21st Century mandrels in a Gen II expander die from Sinclair:
And, on every up stroke of the ram, the OAL gets longer and more trimming is needed. (more than needed)The main difference lies in the fact that you're pulling the expander ball out through the neck from the inside, whereas an expander mandrel is pushed down into the neck from the outside
a bit of an update. Since the time I wrote this I have switched from Redding S bushing dies to conventional one piece full length dies. The reason I switched is that I theorize that a non bushing die would be cut using a one piece reamer in a single operation similar to how a rifle is chambered. This results in the neck being perfectly parallel with the body of the die. With the expander ball removed the only way the neck could be tweaked is if the rim of the case is out of perpendicular and the case would tilt as it is being withdrawn bending the neck to one side. Cleanliness of all the parts is essential with no dirt or debris on the rim of the cases or the shellholderWhen withdrawing a case and pulling the expander ball back through the neck the outer case walls of the neck are not supported by the die walls at that point. If the case cocks in the shellholder becasue of any irregularity of the case rim the expander ball can pull the case neck off center slightly. Using bushing dies with the expander ball removed solved 99% of any concentricity issues I had