I usually don't even come to this section of the forum.
As for the 357Mag being weenie-ized, no, it hasn't been, to my knowledge. 'Course, my knowledge is solely based on the ammo that is turned out on my equipment in my basement with bullets cast in my garage, um, for the most part.
I shoot some jacketed stuff, mostly in rifle loads though.
To put things in perspective though, I have a 357Mag load that leaves a Marlin 1894 at over 2000fps, it uses a Hornady 158gr XTP and a healthy heapin' helpin of Lil' Gun powder. In past experiences with this rifle and the corresponding handgun, a M586 with a 6" barrel, there is usually a 300fps difference in velocity between the two. That being said, I do not shoot Lil' Gun through revolvers because of the issue that Freedom Arms has explored when others have done so.
All of this may seem to be apples and oranges to you folks here BUT, the point I am trying to make is this: "Stop being controlled by others. You are quite capable of having the exact ammo you want, when you want it, in the quantities you want, for the price you want that has been developed by you in your firearms. The system to provide such is called RELOADING! Start today!"
All of that being said, there is no zinc in cast bullets. If you put one ppm in your melt, you will have ruined its ability to fill the mould out and it is of no use to you at that point. Other metals are added to such alloys, antimony, Tin, Linotype, Monotype along with others, to make bullets harder.
FWIW