Heat loss in brass vs iron molds

[Petander]

I tend to inspect a few bullets every other pour or so which might explain the cadence issues.

It's better to keep casting without interruptions.

I was using two (small) Lee 476 molds the other day, first they were on a (recommended) hot plate and after a few pours I was able to alternate them with no downtime at all.

Fill mold #1, put it aside, fill mold #2, put it aside, cut sprue #1, drop bullets #1, fill #1, put it aside, cut sprue #2 etc etc. No need for hot plate during casting. A cool shed temp maybe 50 F.

I prefer brass because I can use three molds alternating like that.

But the OP needs to get his mold temp up. Is the mold clean? Keep casting! (I just got a Svarog alu mold broken in, I thought it was faulty but no, it just needed half a dozen casting sessions to make good slugs. )

[kevin c]

Nearly all my molds are multi cavity aluminum versions, and I do find them finicky temperature wise. I have to speed up a lot if it's colder or windy where I cast (outdoors); I can't inspect and cull each drop like I can when its warmer and windless.

With the semi wad cutter with a deep lube groove I'm casting right now, I have to speed up AND raise the pot temp (PID) 20° AND raise the preheat temp of the mold by 30° (K type probe in a cavity, mold on a hot plate), compared to NLG or shallow lube groove versions of same weight boolits dropped from molds from the same maker and same number of cavities. Even then, a little too slow and I get rounded or wrinkled bands; a little too fast and the sprue crumbles.

So I can confirm that the optimal temp range for an 8 cavity aluminum mold is narrow and hard to maintain in cold casting conditions. Since I need the boolits now, my workaround in this weather (can't cast indoors) is to cast in batches until I lose the light matte frost that I see in the best boolits, then reheat the mold on the hot plate while I inspect and cull the batch. An alternative might be to run hot and cool the sprue using the wet sponge method, though I hate having to break down the mold to oil the steel parts at the end of each session.

[nhyrum]

It's better to keep casting without interruptions.

This. I'll peek at the bullets as they pop out, but I do all my culling at the end, or if the mold starts getting too hot and needs to cool down. Leave the inspection until the end and turning the pot up, at least until you get into a rhythm could help getting up to temp at your cadence.

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[Char-Gar]

I have never had any problems with aluminum molds. They heat up faster and only after one or two casts are ready to go. I never have culled or even looks at the cast bullet until the casting session is over. I then cull and drop the culls and sprus back into the still hot pot. Lee aluminum molds are made from poor quality metal and the six cavity are the only ones of that make I will try to us. I started using NEI molds about 1980. I have found NOE and Accurate molds to be also of high quality.

I use a several tricks developed long ago by members of this board, they are:

I cover the top of the melt with about 1/2 inch of clay kitty litter. This makes fluxing unnecessary after the initial flux.

I place cold ingots on top of the pot lip to prewarm and put them in the pot as needed to keep a proper level. The pot does not lose much, if any temp this way. Yes, I use a bottom pour pot.

I put a shallow metal dish next to the casting pot with a folded cloth in it and water in the bottom. The water will wick up to the top of the cloth and keep it damp. When the cast is done, I turn the mold upside down and touch the spru to the damp cloth, which will cool it instantly. I then cut the spru, dump the bullet on a soft surface and do it again. Bruce B was the guy who came up with the notion of damp cooling the spru.