Here's what I do.
Close the action and slip a rod down the barrel. (firing pin cocked)
Mark it for length at this point.
Get a straw and a short cleaning rod.
Place the bullet in the straw and run it up into the chamber until it stops, gently come up behind the bullet with the cleaning rod just enough to LIGHTLY hold it against the rifling.
Now run the rod back down the barrel and mark it again for length.
Measure the distance between the 2 marks with a decent set of caipers.
This is your over all loaded length touching the lands with ONLY the exact bullet you measured with. There may be some slight variation in bullets even in the same box.
Using the straw allows you to place the bullet into the gun without a lot of fun & games.
When you're finished, a long rod down the barrel will probably be required to pop the bullet out.

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Lynnie, Professional Pest