What I do for my contender and Encore
I size a round and seat a Bullet just deep enough to hold
NO PRIMER/NO POWDER just brass bullet
I light a candle and smoke the bullet
I then carefully put it in the barrel trying not to mar up the smoke
I pull it from the barrel and inspect the smoke it usually is out to much (OAL)
I seat it a bit deeper and repeat(smoking) I do this till I see I am just hitting the lands
I check the OAL and write it down on my note for that barrel and I keep the dummy round in the die set box
it takes a little bit but when done you have the OAL
This will only change when if you change style of Bullets
Everything I own barrels and rifles have their own Dummy besides Me