I purchased a new 457130 two-cavity mold to cast some collar button bullets to try in my Trapdoor Springfields, 1871 Buffalo Classic, and possibly my '74 Sharps. I first cast several with COWW with 2% added tin. They mic'd at about .453"-.454". I next switched to a Lyman #2 alloy to see if I could get the size up to the .457" that I needed and they are advertised to cast with #2. They then mic'd out to about .454"-.455".
I really thought the switch to #2 alloy would make more difference than that. I really don't want to go to a very hard alloy as I plan to use these for some very light charges and figured a softer alloy (properly lubed) might lead the barrels less. Besides, Lyman advertises this mold to cast .457" with #2.
Do I just have a bad mold? Am I missing something about how to increase the size?