OK - read up a lot on this and went through the effort of casting soft lead slugs, then slugging the barrel of my new Sig Sauer .45 ACP. I used a Mitutoyo micrometer and measured the diameter across where the rifling grooves marked the slug. I got .45175, .45185, and .45190. Am I correct in thinking that a .452 sizer is most likely to provide optimal diameter for cast bullets? Thanks in advance.