Just had an opportunity to mess with this a little more. Maybe a little was learned. The original alloy was 20 pounds of 50/50 COWW and Linotype. That should have had 2.25% tin, 7.5% antimony, .13% arsenic and 90.1% lead. When I had the problem with teh circles on the sides of the boolits I added about 4 ounces of pewter. That bumped the tin to about 3.46% and lowered the other percentages only slightly.
It's now 25% COWW, 25% and 50% lead. That should be 1.74% tin, 3.73% antimony, 0.06% arsenic and 94.5% lead. Some of the last session and all of today's tests were done with this alloy.
Yes, I pile up as much on top of the sprue plate as I can to provide the pressure and extra alloy to fill in as the boolit cools.
That was the first thing I tried other than temperature changes. I added straight pewter; couldn't tell any difference
. . . and this is why I use Lee molds as little as possible. Smaller cavities are more difficult for me to get to work than larger ones. The alloy casts fine in other molds, right out of the same pot. I tried 2 other molds, neither of which was aluminum and both picked up the machining marks left by the cherry. I might have a little contamination in the mold from sprue plate lube so I'll clean it thoroughly before any more testing. The mold was not cold. I was having to wait longer than I should for the sprue to freeze so even the sprue plate is pretty hot. The boolits were coming out frosted.
As I started casting this afternoon the mold had been pre-heated on the hot plate. I turned the hot plate up a little hotter than usual to reduce the time it took to get to temperature using alloy. After pouring about 200 boolits I had come to a conclusion that supports 243winxb's comments. I noticed upon opening the sprue plate that there was an aberration at the base of some of the boolits consistently on the side of the cavity opposite the handle end of the mold. At least I found something that was consistent. I cast faster and faster to get the mold hotter but the small spot still remained. As the casting proceeded and the head pressure diminished the spot got worse. At least it was a result I could act on. I started increasing the flow rate to the point that it was as fast as I felt I could manage without having melt go everywhere and still pile up a good puddle over each cavity. This pretty much cured the problem. I'll still clean the mold again. It's a couple of years old and has cast a few thousand boolits at this point. The circled spot on the first boolit is part of the circular flaw. On the third, fourth and fifth that is probably contamination but I didn't see that happen on today's boolits.
I forgot to try pressure casting. Will give that a shot later today and take some pictures.
I took some pictures of the mold before it go hot and was just looking at them. Even though this is a new style mold with huge vent lines I'm starting to think that Popper and Runfiverun nailed it. Some of the vents appear to be clogged with sprue plate lube. That makes sense because this is a new problem with the mold. I'll clean and test again.
David