The powder die was set to maximum bell width...way too wide. I figured out the powder die adjustment and unscrewed it per instructions to just the bare minimum, and now the rounds chamber like a charm.
(Mark, if you're reading this: the hardware is excellent, but the documentation needs a little help here and there.) Alas, I am but a noob, and still figuring things out.
This reloading stuff is pretty neat. I'll load a box of 50 before I head to bed, and then check the powder charge dropping to make sure I'm still getting my three-point-six grains.