Depends on how you define hottest. If I wanted my 357 "loaded for bear" as they used to say I'd use these.
http://www.doubletapammo.com/php/cat...roducts_id=337
A 200 gr hard cast @ 1200 fps from a 4" barrel of 1315 fps from a 6" barrel.
There are some other companies that offer loads with lighter bullets that are faster then DT, but they offer the best speeds with heavier bullets.