No, push it all the way through, then pull it back out again.
If that keeps the necks pretty straight, I'll tell you why it works--and the probable reason you're having troubles.
I'd tried that already, though maybe not with the carbide ball. Anyway, I just went and tried it with the carbide ball on the new stem, just to be sure. I got about .004" runout on both, about the same as I was getting before the die's road trip. Maybe a little less but I only did two cases -- my supply of once-fired 7x57 brass is dwindling!
