while waiting for the reamer, here is something to consider
most 357Maggies have a long throat, allowing you to seat a bullet out to where it can fall out of the case if it is under 220gr or more...
if you can find data for a 360DW, or even a Maxi with the bullets you intend to use, seat them to no longer than the COAL, your capacity will be the same as in the other rounds.
EX/ you have a 180gr SSP load for the 357Max and the book COAL is 1.xxx, if you seat that bullet out to that same length you have the same capacity behind the bullet with Mag brass as with Max brass.
Mag brass is designed to handle pressures near the Max brass, so if you were to keep loads never more than 85-90% of Maxi Maximums, you will be safe. Also note, the CIP maximum Piezo pressure difference is only 1K. So, I'd stick to 85% and run with it.
REMEMBER, that is ONLY if you can seat the bullet OUT to the SAME COAL as the Max load data. If the COAL is not listed or you are unsure, DO NOT USE that data... find other data.
Play safe and keep it under max loads, and find one that shoots well, and you can have confidence to over 100yds....
some folks use their maxi's at 200yds