Several discussions of this. I ran the numbers. A grain of lead alloy is 0.00035 cubic inches, about 0.07" cube. A layer of 0.0002" DIFFERENCE in dia (0.2 width - drive band)for a 20 cal (55gr) is 10gr, 30 cal (165gr) is 30gr, 45 cal (220gr) is 38gr.
So temp ( any) variation that causes as cast dia to change will cause a great difference in total weight.
Edit: got into this discussion as OP thought he could find voids in his cast bullets. A 0.07" cube is big but other variations could hide it, my point. Accuracy - ballistic calculator. Weight does not effect drop due to gravity! Weight does effect inertia! Rotational inertia controls stability and forward inertia (which drops due to wind resistance) increasing TIME that gravity can work on bullet. To simplify, weight variance from A mould makes no difference in POI, a very small % of weight, no change to wind resistance. A large void? Yrs ago I used pin nails to hang bullets to be PCd. Clip off exposed nail. 30/30 RD GCd Lee mould, full loads. NO difference @ 100. I cull as cast bullets visually, not by weight.
So temp ( any) variation that causes as cast dia to change will cause a great difference in total weight.
Edit: got into this discussion as OP thought he could find voids in his cast bullets. A 0.07" cube is big but other variations could hide it, my point. Accuracy - ballistic calculator. Weight does not effect drop due to gravity! Weight does effect inertia! Rotational inertia controls stability and forward inertia (which drops due to wind resistance) increasing TIME that gravity can work on bullet. To simplify, weight variance from A mould makes no difference in POI, a very small % of weight, no change to wind resistance. A large void? Yrs ago I used pin nails to hang bullets to be PCd. Clip off exposed nail. 30/30 RD GCd Lee mould, full loads. NO difference @ 100. I cull as cast bullets visually, not by weight.
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