[arcticap]

So the minnie measures .60625?
What kind of lead was used?
The Lee mold is designed for casting with pure lead. If pure lead isn't used the projectile will be larger in diameter because lead alloys aren't as dense as pure lead is.
But if the mold wasn't made to specifications, then Lee should replace it. While I would guess that's not a very common occurrence, it's a distinct possibility.
Could the aluminum Lee mold have gotten too hot during casting which caused it to expand?
Are electronic calipers or a calibrated instrument being used for measuring? How much do the minnies weigh compared to Lee's stated weight for the cast projectile? Are their diameter & weight consistent? More than one minnie should be measured and weighed to see what their average is.
Another possibility is that the bore is undersized and/or also that the "mic" measurement is off.
And there could also be a combination of more than one of the above.