Will the 0.22 cal seating stem work on the 6BR arbor seating die to make it a 22 Br arbor seating die?
You could but carefully, as there is more room for the bullet nose to not be as straight before entering the stem. It would be preferable to use the proper stem.
I don’t believe the original intent of my post came across. First I need a 22BR seating die, there is no Micron 22BR seating die sold, there is a 6BR however. Now it comes down to a question of design. Looking at the seating stems it is clear that if the outer diameter of the stem was the same for the 22, 6mm, 7mm and perhaps even the 30 then the body of the die would work for each caliber within the BR family. This would create seating dies that were “family” oriented; the BR family, BRA family, “06 family, the 308 family, the x47 family and so on. If the outer diameter of the stem was the same then the issue you bring up would be taken care of I believe. I’m not an engineer/designer so I recognize that there could be many details and issues that I am overlooking or over-simplifying.