just bought a Lyman 575213 OS mould for my 58 cal 1861 Springfield.This is my first time using a pin to make a hollow base bullet.After getting the mould and melt hot it started to drop nice looking bullets with about 30 percent rejects. i weighed the 100 that i poured once it was running and weighed each of them afterwards. The weight spread was from 489-494 grains. is this normal with minnie ball casting?