This is from Redding/Saeco and might help in bullet diameter variables.
Having used a few tons of linotype in my life time I have found casting with straight linotype in molds with sharp edges are a ##### to get the bullets to release. Another factor, the boys at RCBS told me is at what time in the cherries life span was the mold cut? A new one will be larger than an old one for as they are cut the cherry will wear. Multiple cuts in a block will vary as well for it will get hotter as it cuts.
As a test take a 6 cav. mold off it's handles and only heat up one half, when done put the halves together and see how much expansion takes place. A good mold will take this into account with a "known alloy" but with wheel weights today having who knows what expansion/contraction is a crap shoot.
To really screw things up, a guy here on the Island had wheel weight molds and was selling to the tire stores his wheel weights made with whatever he could find.
OP - your problems have been thoughtfully discussed already; best of luck.