Here is a nice article by Larry Willis: http://www.larrywillis.com/OAL.html

And here is one from 6mmbr showing the tool I use, the Hornady LNL gauge: http://www.6mmbr.com/catalog/item/1433308/977259.htm


It is easy to use and I get great results. Measuring by the ogive is the way to go for best results and really knowing where the bullet is to the lands (where the rifling begins).