First, mount your scope correctly. Acetone to remove all oil, then blue Loctite.
Tighten everything as per specs.
Run a clean patch down the barrel, then take it to a range and shoot it.
I "break-in" a barrel, but, I don't know that is necessary.
(I wait for the barrel to cool between each shot)
I'll fire a shot, then use copper solvent with a brush, then a dry patch, and shoot again. (adjusting the scope with every shot)
I do this about 10 times.
I keep doing this until it it hitting where I want it.
Then, I will fire 3-5 rounds, and completely clean the bore.
Almost always, 20 shots will do it, unless I'm not satisfied with the results.
I have a 6.5 CM Kimber that I almost gave up on, until someone gave me 10 rounds of Nosler Trophy Grade 140g Partitions. The rifle went from 3 MOA to sub-MOA with the right ammo.
I've got an old Remington 700 in .30/06 that will send anything 1 MOA - 150-220g.
(You just don't know until you spend time with the rifle.)