Hornady OAL gauge will find the length that touches the rifling and assist in measuring where the ogive (caliber diamater) of your finished round falls.
In terms of determining what's best, you have to shoot bullets to figure that out.
Still happily answering to the call-sign Peetza.
You do not HAVE a soul. You ARE a soul. You HAVE a body.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.