Break in ammo

Id assume your rifle. I’d say yes but others may say no. I usually just load up some seconds’s at a lower powder charge before I start load development.
 
Others here will disagree but don't worry about break in. Just shoot it. Start load development now if you wish. People take.something simple and make it complicated. It will occur naturally. Yes after a few rounds you may see an accuracy improvement as rough spots etc get smoothed etc. Lots of conflicting theories out there.

Keep it simple get or load some ammo take it out and enjoy your rifle. Quit stressing and working about all the nit pockets etc.