I have an aluminum mold made by Accurate. It's a very nice mold, but I have found that the needed casting pace is faster than I'm comfortable with.
I want to try a different material next time. Next mold I order is going to be a 147gr 9mm mold, and I'm trying to decide between brass and iron. Brass strikes me as fragile; it easily tins and warps. Iron/steel seems like a better choice, with the exception that they rust.
To mitigate rust issues, would I be OK storing an iron mold in an ammo can with dessicant in it? Aside from that, what kind of casting pace could I expect to need to maintain with a 4 cavity iron mold? I found that aluminum makes me go faster than I want; I suspect brass would about fit my pace, but there are too many horror stories of warpage and tinning for me to be excited about them, unless someone can convince me otherwise. A good 10 seconds between casts is my comfort zone, FWIW. I will probably get a 4 cavity mold...the weight should be good for me
Getting it out up front, I do not have a hot plate for preheating molds, also no access to any metal coffee cans (which aren't made anymore) to create a makeshift preheating oven. I have no intention of buying one either, because I already can't keep all my tools organized nicely on my workbench, so no additions are going to be made. Any preheating I do is going to be done by dipping the corner of the mold in the melted lead, or not at all and just go straight to casting to get the mold up to temperature. My perception is that brass molds don't react well to this sort of treatment whereas Aluminum and Iron really don't care.