I started with a 9 mm SDB, then added another one for .45......then I started reloading .38 spl, and realized, it is time to upgrade.
Now I have two 550's, one is set for large primer for .45; one for small primer and there I reload 9 mm and .38 spl.
The latter one I do in batches of 500-800 a time, then re-set to 9 mm - takes less then 3 minutes.....as I have two complete set-ups with powder measure, dies etc.
Just pop the connecting rod out, remove the tool head and put the other one in, change shell plate and pins, re-connect the rod, done....