"...They measured 3.19", a difference of 0.15" seemed significant. I was hoping someone might be able to shed some light on this?"
Yeah. It's enough to make a guy suspect book OAL isn't all that critical ain't it?
Back when I started, hardly any data source made any OAL suggestion at all, we figgered out what would work in our own magizines and chambers and developed our charges at that length; we lived.