Casting takes some time, but getting the basics down up front helps, make sure the mold is hot when you start, otherwise it takes a lot of running lead thru it to get it up to temp and all those bullets will be rejects, (I prefer to recycle them as they're done so it doesn't change the pot temp much, a bigger pot makes a difference here too), preheating works wonders, if the mold isn't close to the temp of the casting metal, you'll get wrinkled bullets, once the mold is up to temp and the lead is the right temp, fluxed and cleaned of dross, you'll get a much nicer casting. The bigger the bullet, the more critical keeping things hot is too.
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Tim