Re: Inconsistent Shoulder bump
My guess is that the expander ball is the culprit, at least when combined with LC brass. Here's why: Most sizing dies squeeze the neck down much smaller than needed. The reason is that they are made to work with any and all brands of brass, including the thinnest brass out there. When you run thicker brass through them, you get the problem we're talking about here.
Picture a case with thin neck walls. The die sizes the outside of the neck and it must get it small enough so that the inside is under bullet diameter even after the expander goes through and opens it back up a bit. Now picture that same O.D. but with a case with much thicker neck walls. The O.D. is the same but the I.D. is now ridiculously small, maybe .010 smaller than with the thinner brass.
Then when you try to pull the expander ball out of the neck, it's a real tug-of-war. That LC brass is not only thicker, it's also a tougher alloy than most commercial brass. Remember at that point, the rest of the case is completely unsupported by the die. As you yank the expander out of the neck, the shoulder is pulled upward. The sizing die sets the headspace, but all that yanking on the neck changes it and makes it longer. Lubing the neck or using a carbide sizer button can lessen the friction component, but there is still a fixed amount of upward force that must be used to open up that thick, undersized neck.
I've heard of grinding away the shellholder like mentioned above in order to compensate for a defective die (one that doesn't set the shoulder back far enough). But in this case, what you would be doing is setting the shoulder back too far in an attempt to offset the stretching that the expander is doing. My bet is that you'd get highly inconsistent results. You'd be treating the symptoms rather than addressing the real problem.
The best solution (also the most expensive) would be to get a bushing die which will let you set a proper neck size no matter what kind of brass you are using. Another solution would be to remove the expander ball when sizing the brass, then run the brass through a
Sinclair Expander Die with an
expansion mandrel. That would give you .002 -.003 of neck tension. If you wanted another .001 of tension, you could use a
turning mandrel in the die instead. That would fix your problem for $35.
And it's not like that $35 is wasted on one batch of LC brass. Lots of folks use these same tools even with bushing dies because they (1) give you proper neck tension under any circumstances and (2) they push any neck irregularities to the outside and leave you with a perfectly round and centered I.D. I also use them on all of my new brass for the same reasons.
