When measuring barrel length, is the correct measurement from where the barrel meets the receiver, or is it the entire barrel including the part that threads into the receiver?
from breech to muzzle. Easiest way is to insert cleaning rod into muzzle until it rests against the bolt face (closed bolt) and mark the rod at the muzzle.
On a Remington I measure from the gas hold on the side of the receiver to the muzzle.
Cleaning rod method is always good. They have so many uses. I use a tape measure, tight patch and a cleaning rod to check twist rates.