As I stated earlier, I love Dillon equipment.
However, Dillon Powder Funnels (powder through expanders) are almost always undersized for cast bullets. And they do not have the Lyman "M" die type profile. The Dillon powder funnels place a small flare on the case mouth that is akin to a trumpet bell or a funnel not the straight parallel profile you get with the "M" die profile.
The Dillon expanders generally don't go very deep into the case (unless you set them up to grossly over-expand the case mouth)
The easiest solution is to just obtain a custom powder funnel with the preferred profile. That powder funnel will work with both cast bullets and jacketed bullets, so there's no need to switch back and forth if you decide to load jacketed bullets.
If you start pulling cases out of the progressive press, flare them with a "M" style expander and put them back in the progressive press - you've completely eliminated the advantage of using a progressive press.