Mold Question for the Serious Casters

[challenger_i]

I have used iron molds for nearly 50 years with no issues. I have used aluminum molds with spotty results. So, I would like information, and user experience on Iron vs aluminum vs brass molds.

[Winger Ed.]

I haven't used brass molds. Just Iron & Lee's Alum. ones.

They both work, and work well once you get into the groove with them.
But I prefer Iron. For me, they just seem easier once you get going.

I've worked with Alum. on other things,
and I find it more fragile and I have concerns about messing things up made from it.

[kevin c]

My experience with aluminum pistol bullet gang molds (5 to 8 cavities, 115 to 147 gr nominal dropped weight) is that they can cast well, but that the optimal temp range can be a bit of a challenge to maintain.

[Elpatoloco]

I started with Iron like most folks who have some age on them.

I resisted Aluminum after being disappointed by a few Lee Moulds. I caved in and purchased a mold by Accurate. Aluminum of Quality Manufacture soon became my favorite.
I recently got my first brass Mould from Miha. I dont think you can get a bad bullet out of this mould.

I worried about fragility a bit as well. As far as I can surmise, one has nothing to worry about unless you beat on things with a large hammer or toss your non ferrous mould down the driveway. Again, not speaking of Lee moulds. Im talking about quality made moulds

[Land Owner]

You spend your life reloading to "save money". Then pouring lead boolits from steel and aluminum molds dawns on your reloading experience. After a while, loading cast takes over. The "cost" of fun is reduced with cast. Then you find aluminum and steel molds are not in the same class as beautifully made MiHec brass molds, after you purchase one or two, and you never look back. Shooting cast boolits from beautifully mfg'd and easy to pour brass molds is enlightening and should be experienced - even if you only purchase someone's else's effort.

[ioon44]

I use Accurate and older NEI Aluminum molds, much easier on my hands than heavy iron molds.

[gunther]

Have cast with iron molds since the late 1960's. Still do; have many Lyman's and several 2 and 4 cavity Saeco's. If Lee has a design that suits you, their 6 cavity molds really work well, as do their 2 cavity rifle molds. Never have spent for what seems to me to be a custom mold. Mostly a revolver shooter.

[sigep1764]

I started on aluminum molds and I love them. Light, easy to handle, and if properly luber and cared for will last decades. I do have an iron mold for my 270, it's an RCBS. It too is a great mold. Drops them on open.

My experience with brass is not as good as others here. My MP mold has cavities that stick and it's a 6 cavity mold that should have been made on smaller blocks in my opinion. Its very heavy for being a 22 caliber mold. It is my least favorite to cast with, although it has cast a few thousand boolits.

[Thumbcocker]

You spend your life reloading to "save money". Then pouring lead boolits from steel and aluminum molds dawns on your reloading experience. After a while, loading cast takes over. The "cost" of fun is reduced with cast. Then you find aluminum and steel molds are not in the same class as beautifully made MiHec brass molds, after you purchase one or two, and you never look back. Shooting cast boolits from beautifully mfg'd and easy to pour brass molds is enlightening and should be experienced - even if you only purchase someone's else's effort.

Mirrors my experience exactly. Brass molds are art and a joy to use.

[Bigslug]

They all work fine. I find it to be more a matter of quality of construction than material. Brass does a better job of holding heat if you want to make hollow points, hollow bases, or little bitty calibers. Iron brings that rust management issue to the party. Aluminum is probably the best cost option if you're making solids in the most common calibers and weights.

The main key to success seems to be accepting that, like rifles, every mold is a law unto itself even in the same material, and you have to figure out how to cast for that mold. The three materials themselves hold heat differently, so you can't just robotically run them all the same. My main gauge for temperature control is approximate time it takes for the sprue to freeze, and I use that to set pot temperature and casting speed.

[Rapier]

If you intend to shoot cast bullets in any real volume, suggest you buy RCBS iron moulds, they have a lifetime warranty and when they wear out, which they will, RCBS replaces them without charge. My 358 200 grain FN mould has been replaced 3 times thus far, due to the volume of use. That group of RCBS 358 iron moulds has cast tens of thousands of bullets for matches and practice for me, and is my go to 358 cast bullet for multiple rifles and handguns for hunting and competition. Been casting since 62.
I own two aluminum molds for real low volume bullet casting and for deep sea fishing weights.

[HWooldridge]

They all work fine. I find it to be more a matter of quality of construction than material. Brass does a better job of holding heat if you want to make hollow points, hollow bases, or little bitty calibers. Iron brings that rust management issue to the party. Aluminum is probably the best cost option if you're making solids in the most common calibers and weights.

The main key to success seems to be accepting that, like rifles, every mold is a law unto itself even in the same material, and you have to figure out how to cast for that mold. The three materials themselves hold heat differently, so you can't just robotically run them all the same. My main gauge for temperature control is approximate time it takes for the sprue to freeze, and I use that to set pot temperature and casting speed.

^^This^^

I find the mold material to be somewhat moot and have molds made from several different raw materials. Aluminum heats up faster but obviously loses heat more quickly. Steel or cast iron are good, and so is brass. Aluminum does not rust or corrode quickly so the mold can be left unprotected for a while without damage, and it is lighter on long casting sessions. Brass will tarnish but that doesn’t hurt anything. It’s more important to keep the parting lines and moving parts in good shape.

Some Lee molds are made cheaply - I doubt material changes would make a difference to a poorly made tool.

[35 Rem]

I started about 45 or so years ago with Lee aluminum mainly because of cost. I like them. Then once I got a real job I bought a few RCBS and Lyman iron molds. I liked them too. Later I got Accurate and NOE both aluminum and Brass. Brass makes good bullets but I do NOT like the extra weight. To be honest I never even think about the mold material when casting. They all work the same in my mind. Just melt the alloy and start pouring and adjust anything needed to get good bullets. But as I said, the extra weight of Brass was immediately a negative the 1st time I used my Brass NOE mold. The only reason I bought Brass was that it was the only version in stock at the time.

[challenger_i]

To help narrow the discussion, my question centers on which type will throw a better-quality bullet more consistently. I have very seldom had an iron mold give issues, but I have had little luck with aluminum. I have a bullet design that I wish to have a mold made for and am debating which metal to use. Ergonomics isn't too much of a consideration, as it will be at most a 2-cavity mold.

[sukivel]

They all work fine. I find it to be more a matter of quality of construction than material. Brass does a better job of holding heat if you want to make hollow points, hollow bases, or little bitty calibers. Iron brings that rust management issue to the party. Aluminum is probably the best cost option if you're making solids in the most common calibers and weights.

The main key to success seems to be accepting that, like rifles, every mold is a law unto itself even in the same material, and you have to figure out how to cast for that mold. The three materials themselves hold heat differently, so you can't just robotically run them all the same. My main gauge for temperature control is approximate time it takes for the sprue to freeze, and I use that to set pot temperature and casting speed.

My thoughts almost exactly…


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[sukivel]

To help narrow the discussion, my question centers on which type will throw a better-quality bullet more consistently. I have very seldom had an iron mold give issues, but I have had little luck with aluminum. I have a bullet design that I wish to have a mold made for and am debating which metal to use. Ergonomics isn't too much of a consideration, as it will be at most a 2-cavity mold.

Not sure why you’re not having luck with aluminum but I have custom and inexpensive Lee aluminum molds. Some Lee’s fight you to throw decent bullets, but some drop perfect bullets every time.

Molds are like women, every one is different and needs to be treated differently. Some are good, some are not…


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[ammohead]

To help narrow the discussion, my question centers on which type will throw a better-quality bullet more consistently. I have very seldom had an iron mold give issues, but I have had little luck with aluminum. I have a bullet design that I wish to have a mold made for and am debating which metal to use. Ergonomics isn't too much of a consideration, as it will be at most a 2-cavity mold.

More important than the mould material is the quality of your alloy. For years I strived to find the moulds that cast best. Then I found a source for top quality alloying metals and ALL my moulds started casting excellent boolits. Be picky about what goes in your alloy and cast ingots in large batches for consistency and flux, flux, flux. Good luck.
Oh, brass is my favorite.

[justindad]

To help narrow the discussion, my question centers on which type will throw a better-quality bullet more consistently.

Aluminum heats & cools more quickly, which means the min & max temperatures of the mold over a single casting session will be spread further apart for aluminum than iron. The effect of the temperature range is literally multiplied by the greater coefficient of thermal expansion that aluminum has over iron. So based on theory alone, iron should produce more consistent boolits. Is the effect measureable in the end product? I don’t know.
*
I have four NOE aluminum molds. One NOE brass and one MP brass. I have more iron molds from Saeco, RCBS, and Lyman. I get much better results from iron molds because of their toughness. If I get a smear of lead on the top of the block: with iron, just use a sprue cut and scrape it off; with brass, try to rub it off with your leather glove before it sticks & tins (which ends the casting session for me); with aluminum, hope you see it before it gulls the top of your mold block. I run my molds hot and fast, and iron just survives longer before I have to treat the mold. I don’t like treating molds. That all may just reflect a low skill level on my part.
*
I also get much better bullet ejection from iron molds, which helps keep a more consistent pace and temperature.

[justindad]

More important than the mould material is the quality of your alloy.

Excellent point.

[JonB_in_Glencoe]

I've had spotty results with Iron molds. I like Brass molds, but they are heavy. So that leaves Aluminum, if they are cut right, I prefer them over everything else.