Ole Bloke provided the answer you need.I set up my new Uniflow III 2 nights ago. Hoping to use it soon.
I used the link provided and looked at the micrometer.
How do you know if you need a small or a large?
The RCBS site had no info on that question.
Right now, I just load for pistols. If I ever mass produce rifle rounds, 556 would be the only one.
I am guessing I need the small.