I think its like Madsen said its in the pouring.cut the flow down and see if that works and raise the pot heat,dont worry about frost.have you tried holding against spout and then lifting to get a puddle.it maybe splashing inside.I have been working on that.I just work on it till every thing works.
some people get frustrated and angry,which makes it worse.I have been casting since 1937,first with gilbert toy soldiers.I have singles from Ideal and modern bond double,lyman 4s and lee 1,2 and 6.and a bunch of others going into 1860s.

I bottom pour cast with a Lee custom mold slightly larger than the mold in question and think the mold and alloy is not hot enough. The foward part of the bullet is cooling as the aft is still molten. Because of the volume of the cavity, condensation is rapidly forming which creates the "bubble" cavities that cause the bullets to look corroded. A slow flow from the pot can cause splashing which creates small air cavities also. If you operate the mold at a temperature that is just shy of and to the point of frosty bullets the problem will resolve itself. The mold blocks must be hot to keep the entire cavity molting until the source of heat, the pour, is removed.

Of course, you get to a point were bullet stick or won't drop from the mold because the blocks are too hot. Simply cool your mold by placing it on a damp rag that you keep near the casting site. I develop a rhythm of X amount of casting cycles and Y amount of seconds with the mold on the rag. It makes casting very consistent because you are actually controlling your molds temperature across a very narrow range.

I use Lee molds exclusively and cast from about 30 special order molds for a wide range of calibers.

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Michael

When you pour from a ladle it is generally slower than from the bottom pour spout. On the Lee
production pot there is a way to adjust the flow of lead above the handle you use to open the
spout.

I've had a similar experience as you described and making that adjustment cured the problem.
Just my $.02

I have the identical problem. Solved it by not using the bottom pour when casting 350gr minni balls. I use a ladle. I think it has to do with the fact that the bottom pour method does not fill the mold fast enough and it cools before the pour is completed? In order to get any degree of success with the bottom pour method you got to heat the lead above where it should be and you get frosted bullets and blemishes. Turn down the heat and you get wrinkles and voids. Using the ladle solved these problems for me. I can fill the mold fast enough that I do not get excessive cooling before the pour is completed. I also keep pouring after the sprune is full and I pour directly over the lead pot so as to catch the run off. When pouring the lead shrinks when it hits the mold and sucks the lead off the sprune into the mold, that is why I continue to pour until my ladle is empty. Hope this helps.
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