Cast Iron, Brass or Aluminium - What is your choice?

I prefer aluminum. Though I do have a bunch of brass as well. My brass molds tend to be a bit finicky sometimes.

I usually only do a few boolits (under a hundred) at a time after I finish other lead casting projects so I find aluminum to be more efficient for short periods. If doing a larger boolit making project, I usually prefer iron or brass.

I've never owned or cast with brass moulds ... when I got started it was Lyman and Herters Iron moulds ... then cheap Lee aluminunm moulds dominated what I bought .
It wasn't untill 2015 that I bought my first NOE alumninum mould ...
... that was an epiphany ... A Quality aluminum mould ... it was an amazing thing to cast boolits with and the boolits it dropped were beautiful .

Cast iron , Brass or Aluminum ... That's a tough one ... cast iron is rugged , brass is heavy and aluminum is light . The number of cavities plays a big part , I'm 72 and weight is now a factor , hand / arm strength is less and I can't sit and cast for hours at a time any more ... 1 1/2 or maybe two and I'm ready for a break and some Ibuprofen .
Taking those things into consideration ... I'm going with Aluminum , preferably a 4 cavity NOE in aluminum . I purchased a couple three cavity NOE aluminum moulds and they aren't much lighter than a 4 cavity NOE mould ... the three cavity are cool to pressure cast with a ladle and I like the fact they are unusual .
If I have to pick ... Aluminum !
Gary

I use only H&G moulds. Once up to temp, they produce bullets like nothing else.
I use 4-6-8-10 cavity H&G's. As I get older, they get heavier. A mould guide is required on all of them.
I like them because of their lifetime of use won't even hardly break them in. :) My son and his kids will be using them.
I DO have ONE Lee 6 cavity 130gr 38 gc bullet. I have no idea where I got it but it casts wonderfully.
I load these in 357's and man do they shoot.
I load them with 295 powder and while the recoil is not bad, the muzzle flash is something to behold - especially in a 2" 357!

Still a new guy as I see it…..My molds are Lee Aluminum. I use a Lee 20# pot, PID, and hot plate. I bring everything up to temp and am able to cast usable boolits from the start. I cast several hundred, up to 500 at one setting. 6 cavity molds.

GONRA's Boolit Moulds are all Olde Lyman Cast Iron / Steel or LEE aluminum.
All verk Just Fine for my modest needs...

My olde Potter (?) Electric pot verks Just Great for "bottom pour" casting.

(Mostly "Range Lead" collector auto pistol boolits - nothing fancy.....)

Molds I have are either iron or aluminum. Had 1 mild made of brass but it was heavy and using it just wrecked my hands and wrists.

Iron 1st than aluminum and screw the brass (NEVER AGAIN)/Ed

I cast my first bullets in 1965 with two Lyman iron single and double cavity molds. The first alum block I got, in 1978, in .54 caliber Thompson-Center mold for my unbelievably accurate front loading rifle; to my surprise it worked as well as my iron molds, maybe better. Now I have a mixed few others and like them all. (I shoot, I don't collect reloading tools.)

The thought of buying iron molds because they can withstand more rough handling than alum is astonishing to me; I don't abuse ANY molds!

I find Lee's delightful and inexpensive 6 hole molds to be a delight to use. Like any other molds, how well the boolits may shoot mostly depends on the users guns, shooting, and reloading skills. I no longer enjoy sitting in front of a hot lead pot for hours and Lee's big molds can make a pile of good bullets quickly; I really like that!

I've got all three types but find that the boolits I favor come from the brass MP molds. I usually stick with solid boolits rather than HP because I don't hunt and don't like the extra work with the HP pins.

Recently I've been casting with some of my first molds which were Lyman, SAECO and RCBS one and two cavity. Just wanted to reacquaint myself with the boolits they produced. Except for the time to produce a good pile, they were the easiest to cast with, especially, the SAECO and RCBS. The Lyman molds were mostly acquired early in my casting experience and some had been "well used".

I just finished casting standard .45 auto round nose boolits to compare, with all three brands. Haven't shot any yet but hope to soon. Don't really expect to discover any real differences.

All mine now are aluminum, Lee 6 cav for handgun and NOE 5 cav for rifle. Have had steel molds, Lyman/Ideal and RCBS and they worked fine but were double cavity except for an old Ideal 4 cav 38 WC mold. Went with the 5-6 cav aluminum molds for higher production and less fatigue, an issue for me as a normal casting session is 800-1000 bullets.

Limited experience but so far I prefer brass. Mp hp mold after getting to temperature made me feel like I knew what I was doing.
Less luck with lee molds. They worked but not as nice or clean

If I could wave a wand over my mould pile and change them all to a given metal, it would be brass.

The ones I have seem to need no obsessive cleaning, scrubbing, smoking, mould prepping, or other finagling, like some of the aluminum ones do. And they don’t seem to get cranky or balky in the middle of a casting session like some of the iron ones do, with the lead frosting, shrinking and rounding off bands until the temperature or casting rate or fluxing (or whatever it is) is tweaked or adjusted.

Most of the objections to the alleged weight of brass, as far as I can see, would go away if the blocks were made smaller. For some reason, (maybe to provide a “better” heat capacity?) a lot of brass blocks are larger than Lyman 2-cavity blocks, even though they’re for a 1-cavity mould. They cast well, but so do the small-block integral handled Yankee moulds I have, and the weight of those isn’t noticeably greater than the iron Ideal moulds.

But a good mould is a good mould, whatever it’s made out of.

I have some of all three and they all do exactly what they are supposed to do so I see no advantage of one over the other. I actually have no idea of how many molds I have accumulated over the last 55 years but I can say that I am still short by a few. My next will be one for .348 for the Winchester model71 I just got last month. I also need molds for .32 S&W & L , 25-20 , and at least one for the .22 Hornet/ .218 Bee rifles.