I also have a 357 Max bbl for my Apex but had to get a certain man who cannot be named on this board to do it. It began life as a 222 Remington but was cut down, chambered and bored to the Max.
I'll be interested in hearing of any loading data you come up with that serves you well. I have some at home, am not there currently, but upon return can give you some data if you would like it.