Some molds like the alloy hot but take a long time to cool down, slowing the process. Lowering the thermostat affects bullet quality. So, I keep the alloy hot and cool the bottom (or sprue plate) of the mold, a little bit, on a wet sponge set in a saucer of water. This helps me cast good bullets fast. But, water in the casting area is a danger. Just a drop of water in molten alloy makes an impressive explosion. A safe way to cool the mold between pours is to cool the mold bottom on an aluminum plate or muffin pan. Dick Howes, one of the better offhand shooters at the Old Colony Sportsman's Association, was able to cast bullets fast by having a sponge in a shallow dish of water in the casting area, and pouring-cooling the base of the mold on the wet sponge-removing the bullet-pouring-cooling... He said that the problem in casting fast is keeping the mold cool so that the bullet hardens quickly. (Ken Mollohan's Note: I have had good success using a damp cloth (actually, a clean but discarded bath towel) to rest gang molds on. The cooling is effective, the working area is generous, and there is no liquid water readily available to be a hazard. The damp towel approach also does a decent job of cooling the heavier bullets enough for handling in a reasonable length of time. It also has the advantage of provide the fast, cheap cooling of water without the hazard of explosions from liquid water: when it begins to dry out, just stop long enough to re-wet it at the sink and wring it out before resuming casting.) A. C. Gould, in “THE MODERN AMERICAN RIFLE”, recommends cooling the bottom of the mold in a dish of water between pours. He talks about a person who could cast 12 perfect .45 caliber bullets in a minute, 505 in an hour. This is 30 pounds of 500-grain bullets. I wonder, could A. C. have told a fib? Maybe not. Several shooters on the Internet cast bullet forums report cooling the sprue plate on a wet sponge or rag to cool the mold, and casting lots of bullets quick. Bruce Bannister, on the “Cast Boolits” forum reports: “In one timed run at my normal rate with a SINGLE-cavity Lee .30 mould, I made 159 good bullets in thirty minutes. This translates to over three hundred per hour from a one-banger mould. It's not unusual to get well over 500 good 'uns in an hour from my Lyman or RCBS two-cav jobs, and 400 'bph' is easy. Lyman four-cavity moulds can give me over 1000 per hour on a good day. Casting heavier bullets takes a bit longer due to longer mould-filling-time than is required by lighter boolits."
COOLING THE MOLD
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- Last Post 21 October 2019
You can also use ingots of bullet metal as heat sinks for extended casting sessions. Simply rest the hot molds on the cool ingots as you reach for the next mold when you're casting in tandem. After a while, the ingots will get hot, so feed them to the pot, and set out new, cool ingots to take their place. Unless of course it's necessary to cast at breakneck speed, then you can use the damp cloth routine. BTW, a drop of water needs to be introduced below the surface of the melted lead to cause a steam explosion. A drop on top of the melt will just skitter around on the surface, the same as if it were in a frying pan.
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Getting the thermodynamics of casting to work is a balance. There is no perfect way that works for everybody. I've never really had to use cooling at any point in my casting except the first time I tried a 6 cavity mold. I eventually worked out my timing and pot temperature so I could cast with the 6 cavity and not use cooling. It took some thinking and applying my observations of my own methods to figure where in my casting cadence I had to change, but I got it. I prefer to cast without cooling as I personally see cooling as a variable that I have insufficient control over and mold cooling, for me, dramatically effects the BHN of my bullets and the fill-out of the bullets giving them wide variance.
I'm sure some control that variance way better than I can. I have a balance that works for me and I can maintain pretty even fill-out and BHN of my bullets from a 6 cavity mold... The 6's are much more challenging for me, yet I have certainly read that some casters consider them the easiest to work with!
I cast over 50 years with only 1 and 2 cavity molds before I even tried a 6 cavity mold. I am sure some casters start with 6s and have a ball with them. It wasn't easy for me to make the move, but I got it working.
There is a WIDE variance in methods that will work for usable bullets. My first lead round-balls when I was 6 years old, I cast screaming hot lead into a cold mold. The lead was so hot it was hot enough to warm the mold sufficiently before the lead even began to solidify at all. It worked! It worked just like the guy I copied, Davey Crockett in the books and movies.
Gary
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When casting heavy .40 or .45 rifle bullets, I use a large block of aluminum or copper & hold upside down mould against this for a few seconds.
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I agree with Onandaga (Gary) in that there are a number of ways to cool a mold. I run my pot temperature at 345 degrees celcius (653 degrees F) for all my casting. (Love my PID!) That happens to be the sweet spot for me. Once the mold is up to temperature I find (depending on the weight of the bullet) I may need to leave the mold open for 10 - 15 seconds. Again, depending on the weight/size of the bullet. The smaller 125 grainers I can usually keep rolling at a steady pace. The big 300 grainers require that I hold the mold open for 15 seconds between casts. I'm not in a big hurry when I cast. I enjoy taking my time, having a beer and enjoying the art. Pat Reynolds
If someone else had of done to me what I did to myself . . . I'd have killed him. Humility is an asset. Heh - heh.
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Two things have improved the quantity and quality of my cast bullets in the last 10 years. A hot plate for pre-heating and a small fan, for cooling. I use both a hi-speed squirrel cage fan, ala the Master Caster and a manicure fan as recommended by Mike Venturino.
Duke
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I have had excellent success with water, pyrex baking dish with cotton towel that has soaked up the water. An infinite non-synthetic sponge of sorts.
The towel top layer wicks up water, stays damp. I cast very hot most times, especially with alum molds like lee, bullets finish frosty but perfectly filled out.
Mold will overheat and I you can see the bullet stick or otherwise react from the mold different. Then cooling is needed.
I get a rhythm. Cast 5-6 drops, then with closed mold press bottom of mold on towel. Looks like a chinese laundry for a few seconds. Move mold back to spigot and start pours immediately. I dont have time or patience for a fan to cool things off. Although I do use a hot plate!!
The first few cycles (I dont keep notes on it) usually have a learning curve for the outdoor temps, etc. Will it be 3 drops or 5 before the towel?? How long to I steam it out, in seconds?? It usually takes 15 drops to establish the rhythm.
When those two questions are answered, it flys. I have no safety issues with the water. Its not in liquid state. It doesnt splash to the pot.
Thats my routine, for all types of molds and alloys. Works for me.
That is unless I have an unusually superb alloy and it flows like water. Like heavy in tin makes. Then no cooling needed.
YMMV
See ya later
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The casting 5 or 6 times then cooling is just what I tried the first time I tried to learn with a 6 cavity mold. I did get to a point where I thought I had a good balance and was getting good bullets the first pot-full. A couple more sessions casting that way seemed fine too.
Unfortunately some simple testing and weighing showed a wide variation in bullet weight, diameter and bullet hardness.
That cooling every 5 or six drops shrank the bullet diameter till the mold warmed up again. Close examination under magnification also revealed rounded instead of sharp edges on lube grooves and bases from the cooler mold pours. The hotter pours also had the bullets catching up to correct diameter and heaviest in weight. The biggest concern came when I did hardness testing and found that BHN was all over the place. This combination from testing made the decision that the 3 batches of bullets were actually the worst bullet casting I had ever done in over 50 years and I was furious.
I melted them all made new ingots with warm molds and slow, even air cooling so BHN was steady again for all ingots and started over after I figured where in my casting cadence I should slow down to get the hot mold issue solved.
The next casting session with a fully warmed mold, I started differently. I bottom poured with a large puddled continuous pour for all 6 cavities and watched for the first sign of crystallization in the huge sprue puddle. After that I counted to 6 and the sprue cutter plate opened easily with no smearing. Here is where I changed, with the sprue cutter plate open, I paused a wristwatch monitored 20 seconds before opening the mold and dropping bullets. I also tapped the large sprue directly into the pot, then closed the mold and poured immediately.
This rhythm is currently still the same one I use with my 6 cavity mold, I had concern about dumping the large sprue right back into the pot lowering pot temperature but with continuous running this way there was no significant swing on the thermometer as I was bottom pouring immediately and returning the sprues at the same rate.
My bullets tested very much better for evenness of diameter size, fill-out, weight and hardness. Casting this way also left no big pile of large sprues for the next session and I could cast the whole large pot-full ( about 17 pounds in my Lee 4-20 ) down to 1 inch in the bottom without stopping or fluxing at all. The bullets were much better for me this way than the bullets cast with mold cooling every 5-6 pours.
Gary
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Gary That is a very good description of your method. I have been using a somewhat similar approach but after reading your post, I intend to be a little more rigorous about my pace. I do more than half of my casting each year during January and February. I find that casting cadence when it is 25 degrees is very different from when it is 75 degrees. Normally I need to keep my alloy hotter during the winter months.
Jim
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I found out the hard way that using water to cool a mold is a bad idea and switched to a small fan. Jim
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I have found that the difference from 80 deg to 60 degrees ambient is significant in changing the casting speed and frequency of cooling. Im sure from freezing to summer would be huge!
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I have found that the difference from 80 deg to 60 degrees ambient is significant in changing the casting speed and frequency of cooling. Im sure from freezing to summer would be huge!
Gary, I have noticed all of the traits you mention with my cooling. Absolutely all of them. I live with the results of those traits.
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It is not that one of us is wrong and one is right. Living with what we get like you said is what matters. My 6 cavity mold is 45 cal rifle bullets that weigh 350 grains each. I just did what I had to , to live with the results.
Gary
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I belong to the pre-heat with a hotplate and cool with a manicurists fan group. I use multi-cavity moulds almost exclusively these days (four to six cavities) and like to cast fast. Using the fan not only cools the sprue in two to three seconds, it maintains a steady mould temperature when running my metal at 725 degrees (standard mix is WW's+2% tin).
A side benefit is that it cools the pile of finished bullets so they can be scooped up right after I empty the pot.
I use an RCBS 22 lb. pot and, these days, cast a pot full then quit. I prefer to cast a pot full frequently rather than my old method (when I was younger;) of casting several pot fulls. One weekend I cast 13,000 .45 caliber #68's with my sons melting ingots so I could cast continuously. That is not going to happen again, but that's life, huh?!
I still really enjoy casting. In fact, it's going to be up in the low 30's tomorrow and I may just hit the ol' casting barn and run a pot full...
Dale53
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Guys
All the above described methods work. I am a bit surprised with the experience available, you are still working the neanderthal methods. The small fan does a fair job but the base is a bit harder to cool evenly with a fan. Top of the line is an aluminum finned heat sink from an old style amplifier, coupled with a small fan. For an easy adaptation, a large empty coffee can works well as a heat sink. No steam, always consistant and no need to maintain moisture level. Steel blocks will suffer when using water in any way.
Aluminum finned heat sink from an old style amplifier is easy to get and generaly is attached with only a few fasteners. Fins down, the backs are flat and make good contact with a mould. A small fan pointed at the rest will also cool the sprue quickly.
The coffee can trick is cheaper but requires most bottoms to be thouroughly flattened for good mould contact, to be efficient.
I use both of these cooling methods depending on the situation at hand. The aluminum finned heat sink from an old style amplifier is the most efficient for large cavity casting and I use the coffee can method for my smaller cavity casting. Two mould service is my preferred disipline and I produce huge amounts of very high quality projectiles during a session.
Do yourselves a favor and get set up with one or both of these systems. It will increase your production and you will thank me the first time you knock either one over.
Roy
Shoot often, Shoot well
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I am the kind of neanderthal that sees all your heat sink gimmicks as a junk pile that is unnecessary at all if you have the patience to use a modicum of understanding temperature flow in casting cadence and have the modern man intellect to ponder thermodynamics in casting to the degree that allows you to see logical simple answers are the best answers, not a junk pile of fan and heat sink.
You will probably cut yourself on that junk pile or even knock something important over trying to avoid bumping the junk pile on your crowded bench during casting. Name calling with the thoughtless derogatory word Neanderthal is antisocial too. You are not funny either.
I challenge you to a duel.
Gary
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Guys
All the above described methods work. I am a bit surprised with the experience available, you are still working the neanderthal methods.
Roy
Neanderthal? Hmmmmmmmmm. I find that rather presumptuous of you to say considering the company you're in. Let's play nice. This is just an informative topic with different people sharing different ideas. No need for cynicism.
Pat
If someone else had of done to me what I did to myself . . . I'd have killed him. Humility is an asset. Heh - heh.
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I have found the use of a clock with a large easy to see second sweep hand to greatly reduce weight variations. I watch for sprue puddle to “turn"..then start counting..usually 5 sec. for .22 thru .38.
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I took no offense from Roy's post. Instead I found another pearl of wisdom. When I use the fan I often wished I could cool both sides simultaneously and his heat sink tactic should help with that.
Duke
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... I run my pot temperature at 345 degrees celcius (653 degrees F) for all my casting. (Love my PID!) That happens to be the sweet spot for me.
...
Pat Reynolds
How did you determine the sweet spot temperature?
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