Brass vs. Alum vs. iron mould temps?

[fatelvis]

I just started using a NOE temp probe while casting, and I plan on drilling all my moulds to use it.
My question is: What alloy temp to you cast at, and what temp do you prefer each of your mould materials to run at? Oh how I love toys! Lol... Thanks!

[dragon813gt]

Almost all of mine are brass. And each ones run best at a different alloy temperature. And these temps change depending on the temperature of my garage. Each mold also runs best a different hot plate setting for proper preheating. This changes based on garage temp as well. There is more than one variable involved to determine optimal alloy/mold temperature.

[fatelvis]

I gotcha. Are there ANY generalities, such as brass moulds generally running better hotter than Aluminum and cast moulds?

[MBTcustom]

My knowledge in limited so take it for what it's worth, and anybody feel free to correct me.
All I know is that cast iron molds are medium in weight, and they hold heat very well. This allows very consistent heat if you watch a clock. There is a lot of waiting in between drops with an iron mold. That could be a good thing or a bad thing depending on what you are doing with it.
Aluminum molds are all over the place, but cast good boolits if you are johny on the spot with your timing. They like to be run faster than iron molds, but they heat up and cool down rapidly. They are a pain to try to maintain consistency with but their light weight, and easy handling really covers a lot of sins, and good boolits are very obtainable with a little bit of discipline.
Brass molds are considered by many to be the absolute Cadillac. They like to be run fast they don't lose heat near as quickly as aluminum but you arn't waiting around all teh time like with iron. You are able to get a rhythm going and keep it up easier than the other two. Another thing about brass molds: They are almost as tough as iron, but they do not rust.
The only drawbacks that I have found is that they are heavy as all get out, and arm fatigue is an issue in long sessions, and I have heard that they can warp if you heat them up too hot. Also, even though they hold the heat very well, they are a bear to get up to temperature. Once there, its all good though, and they give you a lot of freedom to be a little sloppy with your timing.
That's my shaky impressions based on feelings and rumors. LOL!

[ElDorado]

I have to agree with Goodsteel about the brass moulds. I have a couple of 4 cavity 45 caliber brass moulds that need to run hotter than steel or aluminum, or it takes them longer to get to the proper temperature. I left one of them on a hot plate too long (the first pour wouldn't solidify) and I did notice some warping, although it is still usable.

Understand that most of my experience with aluminum and steel is with smaller moulds, so some of the extra heating might be caused by the greater mass of these moulds, and not necessarily the material.

[dragon813gt]

I gotcha. Are there ANY generalities, such as brass moulds generally running better hotter than Aluminum and cast moulds?

Brass hollowpoint molds need to be run hot. Both the mold, more the pins, and the alloy. Brass needs to be preheated. Once it's up to temp, it's up to temp and stays there. They can heat soak easily w/ large calibers. And keeping them up to temp w/ tiny 22cal bullets can be an exercise in frustration.

They all have their quirks. I live in the rust belt so I don't have, nor will I ever, any iron molds. I sold off all my Lees for known reasons. Most of mine are brass. I have one aluminium mold from HM Squared that I haven't used yet. My understanding is that it works great for those tiny 22s. And I just ordered an aluminium one from Accurate even though I said I would never order anything but brass. That one is an experiment. Hopefully it works out and I don't need to reorder it in brass.