Brass vs Iron or Aluminum Molds

[Mal Paso]

I wish RCBS made 4 cavity molds.

YES!!!! And Lyman makes great casting molds, if they could only get the holes right.

MP Molds is awesome and I'm sure the brass is chosen for stability and product quality because it doesn't tarnish worth a darn. I've tried! The H&G 503 Clone has a deep and sharp crimp groove and I have had (Tin?) deposits get started on the tip of the groove at the block face and grow to the point the bullets stuck and there were small voids where the deposits were. I kept 3 molds in rotation, cleaning them on a hot plate with a Dremel style brass brush in a non powered holder (Pin Vise} every 2-4,000 boolits. I switched to the MP 6 cavity Aluminum mold for That Boolit when it came out. I have had 2 Brass, 4 cavity devastator molds and never had a problem.

I think Iron are the best but if MP Molds won't do Iron I'll take one of his Brass Cramer molds over any other Hollow Point.

[lar45]

Early on in my casting life I ruined a brass mold the first night I had it. I got it way too hot and didn't notice the lead starting to stick to the top until it was too late. I tried scrubbing and scraping, I even tried a razor blade, but the top of the blocks we're tinned.
I wonder if you could use some cold Bluetooth coat the cavities, face and top.
Now that I built a PID controller, I keep the temp down and haven't ruined another.
I rather prefer aluminum molds now and pre-heat them on a hot plate while the pot is heating up.
For whatever reason, I don't get good bullets out of Lee molds until I smoke them lightly with a BBQ lighter.
Another good way to avoid lead sticking is to use a good sprue plate lube. Cast until your mold is hot and you're getting good bullets, pour one more, cut the sprue, but don't open the mold, get some lube on a rag and wipe down the top of the mold and the top and bottom of the sprue plate. Just don't get any inside the cavities. Re-coat as needed...

[krems]

Lar45 nailed it with how to keep an aluminum mold running good. I keep my Aluminum molds lubed with a good sprue plate lube exactly as above. I like both iron and aluminum molds for various reasons. Big large BPCR bullets meant for long range target shooting with 30-1/or 20-1 alloy are best served with an iron mold and ladle casting. Bullet to bullet weight variations are minimal when casting hotter with these alloys in iron molds. I never could get the target grade bullet weight to weight variation with aluminum molds and big 30-1 alloy bullets. I prefer casting with aluminum molds for all other applications. I like casting with two molds at the same time and also use a hot plate to bring molds up to temperature. I really like the way bullets fall out of aluminum molds. With today’s premium aluminum molds with stainless bushings and alignment pins I don’t worry about wearing out a mold or damaging the alignment holes. A disadvantage I see with aluminum molds is the sprue plate screw and mold handle threads could be damaged easier than on iron molds especially if the threads were cut rather than form tapped. Brass molds always seemed too heavy to me. I rarely use one.