Quoted:
On one toolhead (I have a Dillon 650) I was going to set it up for primary brass processing. Decap in #1, 1200 trimmer in #3 and then a sizing die with an expander ball to clean up the inside of the case mouth in #5. I wanted to use the best kind of sizing die that would be the easiest on the brass, but also give me the most reliability. I have read where some folks use a full length size/decap/expander ball in station #1 to get the case mouth round for trimming. But if the Dillon sizing die that you have to use with the trimmer is a small base die, it looks like it kind of limits options. Am I wrong on this?
To answer your question: I have a 550 and have a Forster .223 FL sizing die in station #1, Station #2 empty, Station #3 has the trimmer die and 1200 trimmer. I set the Dillon trimmer die to just hold the case enough so it doesn't spin when trimming. I don't have any desire for it to resize the case again, just trim. Station #4 has a expander die from 21st century tool (ableit a very tight fit with the trimmer). I also use the UniqueTek toolhead kit to lock the press down, an o-ring under the sizing die. I have no experience with a small base sizing die, so I can't help the OP with that. All I have ever heard was to use a FL sizing die for semi-auto. FWIW