I have 100s of 357s loaded for probably 10 different guns. None of them use a mag primer. Most use WSR, WSP or Rem 7 1/2 primers.
My plinking loads are 5.0 grains of Unique, 158 cast bullet, WSP primer. My cast bullets have either Orange Magic lube, or a Tamarack lube on them. I have not had a problem with dirty barrel or action using Unique.
I have looked but not found my rifle yet. Someday I hope to find a long octagon barreled lever action in .357 mag. I will run WSR primers, a healthy load of AA#9, and the RCBS 180 Silhouette bullet or the LBT 200gr WFN. Both are gas checked bullets and should take deer size game out to 150 yards without problem.
Just a nickles worth of opinion....
Steve