Sorry, got interupted. two other items.
I don't have a metric boat ton of BP reloading experience, but the 357/38Spec load given above doesn't sound especially far fetched, it is "about" what I would expect. Roughly. On the third tuesday of months with no R in the name...but I am not calling BS. Look for the biggest possible case volume for whatever bore diameter you select.
Second, yes, I think my dedicated BP guns are all going to be SS. I may send one in to get Parkerized or some such, but yep, I'll be packing Stainless mostly thank you.