Last year I bought a new .434 double cavity mold from NOE. When starting to cast from a cold mold, the first 3 or 4 bullets would drop at .434. But , as the mold heated up, the bullets drooped bigger & bigger. When up to operating temp, they stabilized & dropped at 439+ to .440, & stayed that way. I contacted NOE & they replaced the mold, no problem.The new mold works perfectly.
I still have the old mold, & guess it is only good for casting sinkers. I've been casting for over 60 yrs & have never had a mold act this way.