Several years ago,a friend of mine had two molds, a Lyman and a Lee that would not cast bullets anywhere near the same weight. Both molds were of the same caliber which I can't remember what the caliber was, but both were large caliber molds.
We got the idea to apply vibration to the molds as they were being filled. We found an old electric shaver that did produce a pretty good rate of vibration. It was a two- man job, one to hold the razor against the mold and the other man to hold and fill the mold. We cast several bullets from each mold and after a cool down we began our weighing. The bullets from the Lyman mold were terrific, hardly varying in weight at all. We then weighed the bullets from the Lee mold, they were horrible in weight variation. I have never experimented with this technique since and wonder if anyone else has tried such an experiment.
David a. Cogburn