I've been casting boolits for nearly 30 years but this is the first time I've encountered the phenomenon of boolits increasing their diameter after a couple of years of storage. To be specific, a couple of years ago I cast up several hundred 44 cal boolits, both PB and GC style, using Mihec brass moulds, model 432-640 RF in solid configuration (I also have the pins required to make HP boolits but I've noted this problem only with solids since all my HP boolits have already been lubed and sized and seem to have retained their sized diameter). Specifically, the boolits as they dropped from the mould miked, as I recall, between .432 to .433 in diameter, consistent with the diameter marked on the mould. Not having the time or need to lube and size them at that time, I stored them in plastic jars in my garage where the temperature probably varied between 40 degrees F as a low to 80 degrees F as a high. A few days ago I decided to lube and size a few of these boolits and to my surprise, both the GC and PB boolits are now miking at between .434 to .436, making it difficult to size them to even a reasonably large diameter of .432! My alloy is what I've used for years, my own approximation of 'Hard Ball' or 'Taracorp Magnum' alloy - 92/6/2 (Lead/Antimony/Tin). I've made up this alloy in 100 to 200 lb batches so the composition ought to be reasonably consistent from ingot to ingot and as I say, I haven't seen this sort of diameter increase with any other of the boolits I cast for several different calibers (380Auto, 9mm, 38Spl/357Mag, 40S&W/10mm, 44Spl/44Mag, 45Auto, 30-06, 308Win, 7.62X39, 45/70). My melt is PID controlled at between 700-750 degrees F, bottom poured from a Lee 20 pot with the mould preheated on a hot plate, and my boolits in general are just slightly dulled, not heavily frosted as one would expect if the temperature of the melt was too high but also not bright and shiny with incomplete fill as one would expect with too low a casting temperature. Any suggestions as to why this might be happening with this particular boolit would be greatly appreciated.
sleeper1428