Casting With My First Brass Mold

[rr2241tx]

I need help. My brand new MiHec 454-308 Brass 4 Cavity Solid mold came last week and it was beautiful. All my prior casting experience is with iron or aluminum molds, so I read up on brass molds. In 4 hours I only made 65 keepers and not all of those were consecutive. I missed something critical.

[mold maker]

Brass eats heat. Pre heat the cleaned mold and cast faster to keep it hot.
When ya get the right combo, you'll be amazed.

[JWNathan]

Great to know, just got the same mold from MiHec for my first brass. Looks killer, hope I get it figured out!
-Jesse

[dragon813gt]

They like heat, a lot of it. My normal process is to clean w/ carb cleaner, heat cycle three to four times in the toaster over, and then lube everything up. Preheat the mold on a hot plate while the pot is coming up to temp. When the sprue plate lube starts smoking you know it's getting close to temp. Don't look at the first few rounds of casting to see if they are good bullets. Just keep casting and sort at the end. As long as they're releasing from the mold you are good.

[Oreo]

Brass likes heat. Brass holds heat pretty well so it's not like you need to cast at lightening speed. You just need to get the mold hot enough in the first place. After that it's pretty forgiving with regard to pace.

[gtgeorge]

That mold needs to be HOT to start as others have said. The pour needs to be quick and hot as well to fill that big boy out well with a big sprue. It will retain heat well and you can slow down a bit when it starts throwing good bullets though. I have also found a good cleaning with hot soapy water and then heat cycled on a hot plate a couple times before casting. It will do better every time you cast with it too.

[pdgh59]

Have your alloy at 800 degrees before you start pouring. I broke in a new brass mould last Saturday and hardly had any wrinkled boolits. It took about twenty castings before the boolits started to look good.

[dragon813gt]

Have your alloy at 800 degrees before you start pouring.
Way to hot. There is no reason to go above 725. You are going to lose any tin in the alloy it you run it up to 800. Mold temp is the key. Running the alloy at an elevated temp is just compensating for a cool mold.

[Oreo]

I've cast in MP molds using 800°f. It mostly works but I found it was completely unnecessary to have the alloy that hot if I got the mold up to proper temp. Then I was able to back the alloy temp down to 675° or so.

[rr2241tx]

My spout freezes when the pot temp goes below 700 indicated, so I will heat cycle the mold a few times then try pre-heating on a higher setting. I'd read all sorts of dire warnings about warping brass molds so turned my hotplate down some from the setting I use for iron molds. That big chunk of brass sure hots up my gloves.

[runfiverun]

heat cycling it through casting a few times gives the cavity's a patina. [it does it on aluminum and steel molds too]
you want that oxidization.

and you want to know your real temp, not what the dial shows.
pretty much any kind of lead alloy with tin and antimony in it should be fully liquidous and flow easily at 700-f.

[Maximumbob54]

I can't cast fast enough I guess because I have to have at least 750 degree lead to cast with brass. Maybe it's less the brass so much as the HP pins.

[dragon813gt]

I can't cast fast enough I guess because I have to have at least 750 degree lead to cast with brass. Maybe it's less the brass so much as the HP pins.

The mold isn't up to temp if this is the case. I went through the same issues thinking I had to run the alloy hotter. Once the mold is up to temp, even w/ hollow point pins, there is no reason to go above 725. And I only run it that hot when it's below freezing in my garage.

Once the mold is up to temp it will stay there. You have to cast a little faster if it's a HP mold. But it's still not a race. One of the things I like the most about brass is I can cast at a leisurely pace.

[pdgh59]

I sat my brass mould on the furnace while the alloy heated up to 800c. The alloy was covered with sawdust that charred. Alloy poured well and no surplus tin.

[dondiego]

800c! That is HOT!

[rr2241tx]

You guys really came through. It rained a little here, maybe you saw it on the news? Before the rain, I cranked up the hotplate and by the time my pot was up to temp the mold was hot enough that it melted the lead plug out of the roll pin sprue plate stopper. That might have been a little bit hotter than necessary but it did create some nice "patina". The first pour took 90 seconds to freeze the sprue. I ran the pot almost dry without noticing and the only dwarfs were my timing errors that slopped over into a hole other than the one I was filling on purpose. The second pot went even better. I am going to need to go to the gym though, that 4 cavity mold is heavy after a while. Just for the record, I was running a Lee Pro 4-20 with the threaded replacement needle and did not lose one drop of leakage the whole session. I used a piece of 2X4 for a "mold guide". It charred a little but was vastly superior to the factory guide.

[dragon813gt]

Threaded needle for the 4-20? Is this a new part from Lee or am I just having a brain fart.

I've never used the mold guide. I use plywood cut to width and stack them up to get the correct height. They become nice and smooth after some use. Not having to hold the mold while pouring is an arm saver.

[rr2241tx]

I got this part here: http://www.titanreloading.com/service-parts/mold-and-melter-parts/lee-el3427-pro-420-valve-rod. The part with the big headed adjustment screw that came with the pot just never would open sufficiently nor close reliably for me. I got the new part and a new spout and ran them together with some white auto compound for a minute or two until I had 100% contact between the rod and seat. I put a pair of hex nuts on either side of the handle assembly and once I had the open and shut positions set, jammed the setting with the outboard nuts. Not one drip since and no accidental disengagements either.

[GMT210]

Take a look at this thread, works very well for me.

http://castboolits.gunloads.com/showthread.php?215409-Brass-Mold-Prepping-Cleaning-Lead-Removal-Patina-amp-Smoking