We shoot A LOT of 357 in Rifles.
(haven’t read the entire thread)
I assume you are going to use for medium size game around 200 yards.
We shoot A LOT of 357. 180gr XTP at 200 yards or closer should be fine and can be loaded quite accurate. We have had really good results with HS-6.
I don’t have any expience with lead in 357 but do know that people get really good accuracy with 200gr lead to 200 yards also but your going to be traveling much slower.
It’s a single shot so I believe some manufactures make spire point bullets that you can get much better BC numbers out of. Even with those though your going to run out of steam REALLY fast much past 200 yards.
Good luck!