Here's something that may help out those considering casting their own and those new to casting. There is no shortage of "internet wisdom" that suggests to get good mold fill-out to simply crank up the heat, get the alloy in the pot as hot as you can. This is very poor advice on a couple of counts.
First, if your using an alloy that has tin (Sn) in it by cranking up the heat you are defeating the main purpose of having Sn in the alloy. Tin will reduce the surface tension of the alloy going into the mold enabling good fill-out of the molds details, past about 750 degrees Sn looses much of it's ability to do this plus the Sn itself oxidizes much faster on the surface of the melt at the higher temps.
Next and probably even more important is that with the alloy temp much hotter than needed you need to wait longer and longer between pours for the alloy inside the mold to cool enough to open the mold and drop the bullets as your mold gets hotter and hotter. You also need to wait longer for the sprue puddle to freeze to open the sprue plate. All this extra and un-needed waiting slows down the casting and reduces the amount of bullets that can be produced in a casting session.
Good advice for new casters is to run the alloy temp at about 100 degrees over full liquidus temp of the alloy your using. For most common bullet alloys this will be around 700 degrees. If your casting with pure Lead (Pb) for muzzle loaders about 750 degrees is plenty of heat and will also help with limiting oxidation of the Pb.
As a new caster one of the first things you'll learn is that for quality well filled out bullets mold temp is critical. You'll never get good fill-out or wrinkle free bullets with a mold that is too cool. Likewise a mold that is too hot will be detrimental to casting quality bullets. Never pause between mold fills to admire your new creations, your mold is cooling off. Plenty of time to admire them when your finished casting.
Most molds will cast well at around 400 degrees, a temp that is below the solidus temp of the alloy but hot enough to allow good fill-out. That temp will vary depending on the size of the mold blocks and the mold material and the size of the cavities of the bullets you are casting but the mold temp will be in this range.
Logic will tell you that cranking up the heat is not the logical answer to well filled out bullets. If your pot temp is 700 degrees and a mold temp of about 400 degrees will cast well your alloy is 300 degrees hotter than needed mold temp. That 300 degree difference is more than enough to get and keep your mold at a good casting temp.
For small bullets such as 22's in large blocks (comparative to cavity size) or hollow point bullets I splurge with the heat and "crank it up" to 720 - 725 degrees. Any hotter isn't needed, isn't good for the alloy and will slow down your casting. For mold temp don't look at it as pouring lead into the mold, look at as pouring heat. The larger the bullet your casting and the smaller the mold blocks the faster the mold heats. In addition aluminum molds cool far faster between pours than either iron or brass molds but even with aluminum you don't need a hotter pot temp, you just need to keep casting at a steady pace.
First, if your using an alloy that has tin (Sn) in it by cranking up the heat you are defeating the main purpose of having Sn in the alloy. Tin will reduce the surface tension of the alloy going into the mold enabling good fill-out of the molds details, past about 750 degrees Sn looses much of it's ability to do this plus the Sn itself oxidizes much faster on the surface of the melt at the higher temps.
Next and probably even more important is that with the alloy temp much hotter than needed you need to wait longer and longer between pours for the alloy inside the mold to cool enough to open the mold and drop the bullets as your mold gets hotter and hotter. You also need to wait longer for the sprue puddle to freeze to open the sprue plate. All this extra and un-needed waiting slows down the casting and reduces the amount of bullets that can be produced in a casting session.
Good advice for new casters is to run the alloy temp at about 100 degrees over full liquidus temp of the alloy your using. For most common bullet alloys this will be around 700 degrees. If your casting with pure Lead (Pb) for muzzle loaders about 750 degrees is plenty of heat and will also help with limiting oxidation of the Pb.
As a new caster one of the first things you'll learn is that for quality well filled out bullets mold temp is critical. You'll never get good fill-out or wrinkle free bullets with a mold that is too cool. Likewise a mold that is too hot will be detrimental to casting quality bullets. Never pause between mold fills to admire your new creations, your mold is cooling off. Plenty of time to admire them when your finished casting.
Most molds will cast well at around 400 degrees, a temp that is below the solidus temp of the alloy but hot enough to allow good fill-out. That temp will vary depending on the size of the mold blocks and the mold material and the size of the cavities of the bullets you are casting but the mold temp will be in this range.
Logic will tell you that cranking up the heat is not the logical answer to well filled out bullets. If your pot temp is 700 degrees and a mold temp of about 400 degrees will cast well your alloy is 300 degrees hotter than needed mold temp. That 300 degree difference is more than enough to get and keep your mold at a good casting temp.
For small bullets such as 22's in large blocks (comparative to cavity size) or hollow point bullets I splurge with the heat and "crank it up" to 720 - 725 degrees. Any hotter isn't needed, isn't good for the alloy and will slow down your casting. For mold temp don't look at it as pouring lead into the mold, look at as pouring heat. The larger the bullet your casting and the smaller the mold blocks the faster the mold heats. In addition aluminum molds cool far faster between pours than either iron or brass molds but even with aluminum you don't need a hotter pot temp, you just need to keep casting at a steady pace.
