[Adamantium]

When in doubt use a round of factory ammunition as a guide, I did this for years before I owned calipers. To be honest the amount to taper crimp you put on with your seating die will be far more important to reliability than OAL as long as you are in the ballpark.

I think Accurate's manual deals with OAL best when they say,

SPECIAL NOTE ON CARTRIDGE OVERALL LENGTH “COL”
It is important to note that the SAAMI “COL” values are for the firearms and ammunition manufacturers industry and must be seen as a guideline only.
The individual reloader is free to adjust this dimension to suit their particular firearm-component-weapon combination.
This parameter is determined by various dimensions such as
1) magazine length (space),
2) freebore-lead dimensions of the barrel,
3) ogive or profile of the projectile and
4) position of cannelure or crimp groove