Lyman Four Cavity Mold Modifications

[Hueyville]

About 25 years ago one of my tutors in the world of firearms closed down his commercial casting business. He had been casting since WW II and had it pretty much figured out. Between feeding bullets to his business and three sons all competitive IPSC shooters, I took every opportunity to hang around and help. Learned a lot and when he retired from commercial casting he sold me much of his extra molds and equipment. Learned how to make my own bullet lube, cast fast and turn out quality product that would win at matches from him. Pictured below a Lyman four cavity mold from this lot. Hope this doesn't cause anyone to have a stroke seeing what some will do to a set of mold blocks.

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Machined down the bottom and machined all the holes every side to allow the mold to cool at rate preferred. Till purchased my on mill, lathe, surfacing machines finding a machine shop willing to do small jobs at affordable price was tough. Paid to have one four cavity set done the same and generally fussed about or ignored the others as much as possible. Now have done most of my four cavity iron molds very similar or the same. Usually I sneak up and take small bites and stop when mold runs good at my temperature and alloy it's used for. Each is a bit different but not by much.

Currently have two new sets of Lyman Four cavity molds sitting at work and never been run but planning to do step one first which is a shallow milling of divot's and machining a small portion off bottom of mold. Have dug around old posts a bit but before I go off all crazy on two new sets of molds thought I would ask what others have done to aid in mold modifications to speed up cooling. Don't like fans other than ventilation or monkeying with other variables that much. Have three bottom pour furnaces, one for hard alloy, one for wheel weights and one for soft lead. Each is turned to same setting for alloy then each mold is machined till runs well at my proper temperature for each alloy.

There is no keeping up with settings for each mold, just turn on pot till pointer on dial lines up with sharpie mark and run fast as I can. Probably why have broken the sprue cams on my big Lee six cavity molds. Have steel cams on the way for the ones that have issues breaking but as fast as my molds cool it is hard to cut sprue's before mold cools off. My idea is keeping it all simple by doing it the hard way initially. Adjust mold blocks to my style, speed and alloy rather than monkey with the variables for each mold. Except for some of the heaviest bullet weight six cavity Lee's this has worked great. But the over 250 grain Lee molds don't like to run my way without the occasional broken cam. Sure the steel cams will fix that issue but still wanted to ask about different people's ways of modifying the actual mold to run at desired temperature.

[M-Tecs]

Very interesting. Thanks for posting.

[mold maker]

Except for adding some set screws, and screws for the cutter to wedge against, I've never made mods to the molds. I can see where those mods would have the benefit described.
Most of my problems involve keeping the molds hot enough. I'm getting slower in my advancing years.

[Hueyville]

Seldom have issues with heating as modified molds heat faster. Usually have two molds and sometimes three running at same time and most are four or two cavity Lyman sets. First few sets 30 some years ago were Lee aluminum single hole but was 15 years old and trying to get running with casting and loading from scratch after local game warden mentored me along in his shop starting at age 13. Luckily he was the only law around and could get to his house mostly using dirt roads as eventually let me use his equipment unsupervised long as brought own components. Due to blend of cost and function moved to two cavity Lyman then to the four hole molds when really got chugging by early 20's.

Less mass takes less time to heat up and less to cool. Hanging out in a small commercial shop with manual casting equipment quality was necessary to sell but had to move fast to make money. Hot alloy fills the mold out evenly and if able to cool it quickly then casting runs really fast. Each alloy is kept pretty close to its desired characteristics with little variation as possible. Each furnace runs as hot as possible for its alloy without frosting. Frosting aggregates me as well as unfilled holes and divots where sprue is cut.


Set one mold on the preheat rack of furnace and turn on to heat and find chore to do. Soon as start casting set second mold on rack to heat. At some point mold running will overheat and usually show with sprue smear or divots. First indication of overheating swap to second mold. Run till it shows signs of getting too hot then back to mold number one. If run a long session may even put third mold into rotation. Just for organization when work a three mold rotation often use a two hole Lyman or six cavity Lee as third and one of the molds water drop the bullets so my padded table top does not get too cluttered with bullets. As I run and oldest pile worked cools they get scooped off into a container and roll all left on table to rear.


Have limited lifetime and all the bullets have to be lubed, sized, loaded and shot. Thus when loading like to run fast. Have multiple progressive presses so don't have to do caliber changes often and have figured out least time taken changing any setup is more time producing. Why have three pots and waiting on number four. Want to add a Mag 25 to the pair of Mag 20's. Want to add fourth alloy to selection so it will get its own pot so don't ever have to run one dry. When casting have a line of ingots on back of pot warming and feed in as fast as pot will take so furnace pours with same flow and everything stays consistent.

Butchering my mold blocks really does allow significant speed over un-butchered. Even if cast a little slow does not hurt the final product. Have yet to see a down side so figured more people whacked their molds up to decrease mass and increase surface area. Would have not figured out myself but a sly ol man who was full of tricks showed me his tricks. Another great thing with bigger molds is how much weight they lose. Running a four hole mold that has lost half it's weight makes long sessions much less tiring. Would like to see any other ways people have tried to skin similar cat by slicing and dicing. One of the new four hole molds would not upset me to take a chance on a new technique and if died in process would not cry as was cheap enough to experiment with. If worked better would happily change my ways.