Hey Dusty, if you think your wife is the absolute expert on detecting AB's, we should put her into a challenge match with my wife, who appears to me to the expert.
Actually, I find Joeb's information fascinating. It makes no intuitive sense to me that it should be true. You would expect that errors in weight due to mold temperature variation would be proportional to the volume of each cavity. You would expect errors due to mold closing would be a two DOF function of profile area and profile length (out-of-round error and feathering, respectively). You would expect geometric errors to be proportional to alloy density if you replicated them with different alloys. The whole thing is weird. It's as if there were a tendency for different error types to to compensate for one another in some way, but I can't imagine what that would be?
So, naturally, questions arise: The premise of Joeb's point seems to be: if you are doing everything right, this results. Soooo, acid test, how do bullets meeting this criteria shoot compared with those that don't? One would presume a .457 bullet could tolerate greater weight variation than a .224 bullet before the effects show up on the target.
I now routinely drill and tap a short blind hole in a corner of my mold blocks to accept a thermocouple trapped under a screw (aluminum screw for aluminum block, steel for iron blocks). This lets me use temperature to time pours. It does a very good job of keeping bullet dimensions consistent. Joeb's data indicates that, should I raise or lower the mean mold temperature I pour at, the cast weight variation would remain the same. Very unexpected, if true.
A second set of questions pertain to a portion of the premise, that the bullets be "visually perfect". If you try both bottom pour and ladle pour methods, you quickly see a difference in the filled appearance of the bullets. Because the velocity of the molten alloy from a full bottom pour pot is higher and puts more inertia into the lead, it tends to yield sharper fill details. Even so, the bottom pour bullets aren't more accurate. "Constancy is insight", according to Lao Tzu, and, as we all know, it is what produces cast bullet shooting performance. Also, some alloys fill molds better than others, regardless of pour method. So then, what defines "visually perfect" in this context? Is it just consistent appearance? Does it change with alloy and production method? If you do accept a change for alloy and method, does that change the distributions and standard deviation in weight?
Joeb, do you have any additional information about the alloys and casting temperatures and pour methods involved so we can see if there is any pattern there? Or have you already made that comparison? Like you, I don't see a reason your numbers should be true, but we can't just shoot the data. Well, OK, maybe we could, but you know what I mean.
Thanks,
Nick
